  United States Court of Appeals
      for the Federal Circuit
                ______________________

                 CHEMTALL, INC.,
                  Plaintiff-Appellant

                          v.

                  UNITED STATES,
                  Defendant-Appellee
                ______________________

                      2016-2380
                ______________________

   Appeal from the United States Court of International
Trade in No. 1:12-cv-00079-LMG, Judge Leo M. Gordon.
                 ______________________

             Decided: December 21, 2017
               ______________________

      MATTHEW R. NICELY, Hughes Hubbard & Reed
LLP, Washington, DC, argued for plaintiff-appellant.
Also represented by DANIEL MARTIN WITKOWSKI; ROBERT
L. LAFRANKIE, AARON MICHAEL MARX, Crowell & Moring,
LLP, Washington, DC.

      ERIC LAUFGRABEN, Commercial Litigation Branch,
Civil Division, United States Department of Justice,
Washington, DC, argued for defendant-appellee. Also
represented by CHAD A. READLER, JEANNE E. DAVIDSON,
CLAUDIA BURKE; PAULA S. SMITH, Office of the Assistant
Chief Counsel, United States Bureau of Customs and
2                          CHEMTALL, INC. v. UNITED STATES




Border Protection, United States Department of Home-
land Security, New York, NY.
                 ______________________

     Before DYK, BRYSON, and REYNA, Circuit Judges.
BRYSON, Circuit Judge.
    This customs classification case requires us to define
the term “amide” as used in the Harmonized Tariff
Schedule of the United States (“HTSUS”). In particular,
we are called on to distinguish between “Amides” and
“Other” in a heading of the HTSUS that covers amides,
their derivatives, and salts thereof. Chemtall, Inc. ap-
peals from a decision of the Court of International Trade
holding that Chemtall’s product, acrylamido tertiary butyl
sulfonic acid (“ATBS”), is not an amide, but is a derivative
of an amide. Chemtall, Inc. v. United States, 179 F. Supp.
3d 1200 (Ct. Int’l Trade 2016). We affirm.
                             I
                             A
    Heading 2924 of the HTSUS covers carboxyamide-
function compounds and amide-function compounds of
carbonic acids. All amides of this type contain an amide
functional group consisting of a carbon atom (C), an
oxygen atom (O), and a nitrogen atom (N), in which there
is a double bond between the carbon and oxygen atoms,
and a single bond between the carbon and nitrogen atoms.
This amide functional group contains three substituents,
or radicals (designated as R1, R2, and R3), one of which is
bonded to the carbon atom and two of which are bonded to
the nitrogen atom. Each of the radicals R2 and R3 can be
a hydrogen atom (H) or a group of atoms beginning with a
carbon atom bonded to the nitrogen atom. The functional
group has the following general structure:
CHEMTALL, INC. v. UNITED STATES                         3




    An amide with the general structure depicted above
can be a primary, secondary, or tertiary amide. An amide
in which the nitrogen atom is bonded to two hydrogen
atoms (at locations R2 and R3) and a carbon atom is called
a primary amide; it has the general structure R–CONH2.
An amide in which the nitrogen atom is bonded to one
hydrogen atom and two structures each beginning with a
carbon atom is called a secondary amide; it has the gen-
eral structure R–CONHR'. An amide in which the nitro-
gen atom is bonded to three structures each beginning
with a carbon atom is called a tertiary amide; it has the
general structure R–CONR'2. The structures of these
three categories of amides can be depicted as follows:




L.G. Wade, Jr., Organic Chemistry 984 (8th ed. 2013); see
also Marc Loudon & Jim Parise, Organic Chemistry 1048
(6th ed. 2016).
    The parties agree that in order to be considered an
amide under the tariff schedule, a compound must contain
an amide functional group. The central issue in this case
is what elements may be included in the radical groups so
that the entire compound will be considered an amide and
when, with the addition of other elements, the compound
ceases to be an amide.
4                          CHEMTALL, INC. v. UNITED STATES




                             B
    The dispute in this case involves the proper classifica-
tion of 38 entries of ATBS during 2010 and 2011. ATBS
contains (1) an amide functional group and has a hydro-
carbyl group in the R1 position; (2) a hydrogen atom in the
R2 position; and (3) a compound containing hydrogen,
carbon, oxygen, and sulfur (S) atoms in the R3 position.
The structure of ATBS can be depicted as follows:




The question before the court is whether the addition of
the SO3H group as part of the R3 radical means that the
compound is not an amide within the meaning of the
HTSUS, but instead is a derivative of an amide.
    The parties do not dispute that ATBS is properly cat-
egorized under heading 2924 of the HTSUS. Heading
2924 is divided into two categories. The first category,
which is titled “Acyclic amides (including acyclic carba-
mates) and their derivatives; salts thereof,” encompasses
subheadings 2924.11 through 2924.19. The second cate-
gory, which is titled “Cyclic amides (including cyclic
carbamates) and their derivatives; salts thereof,” encom-
passes subheadings 2924.21 through 2924.29. The dis-
tinction between acyclic and cyclic amides turns on
whether the compound includes a cyclic structure of
atoms. Because ATBS does not contain such a ring struc-
ture, it is acyclic.
   The part of subheading 2924 that addresses acyclic
amides reads as follows:
CHEMTALL, INC. v. UNITED STATES                        5




At the time of the entries, Chemtall classified its ship-
ments of ATBS under subheading 2924.19.11.10, as
“Other: Amides: Acrylamide,” subject to a 3.7% duty rate.
U.S. Customs and Border Protection (“Customs”) disa-
greed. In notices of action issued in early 2011, Customs
notified Chemtall that it had determined that ATBS was
not an amide under subheading 2924.19.11 (“Amides”),
but    should    be    reclassified   under    subheading
2924.19.80.00 (“Other”), which carries a 6.5% duty rate.
Chemtall protested the reclassification, and Customs
denied the protests. Customs ruled that ATBS was not an
acyclic amide, but a sulphonated derivative of an acyclic
amide and therefore did not qualify as an “Amide” classi-
fiable under subheading 2924.19.11.
    Chemtall filed a complaint in the Court of Interna-
tional Trade seeking review of Customs’ decision. In that
action, Chemtall argued that the definition of an amide
requires that the three radical groups attached to the
amide functional group must consist of either hydrogen, a
6                          CHEMTALL, INC. v. UNITED STATES




hydrocarbyl group, or what Chemtall referred to as a
“substituted hydrocarbyl” group. Chemtall contended
that the radical in the R3 position of ATBS, which con-
tains sulfur and oxygen, is a substituted hydrocarbyl
group, and that ATBS is therefore an amide.
    The government argued that the radicals attached to
an amide functional group may consist only of hydrogen,
alkyl groups, or aryl groups. Both alkyl and aryl groups
are hydrocarbyls and do not contain sulfur or oxygen, so
ATBS is excluded from the government’s definition of
“amide.”
    On cross-motions for summary judgment, the Court of
International Trade adopted the government’s definition
of the term amide and held that ATBS is properly catego-
rized under subheading 2924.19.80.00. Chemtall timely
appealed.
                            II
                            A
    In reviewing a classification ruling, we have “an inde-
pendent responsibility to decide the legal issue of the
proper meaning and scope of HTSUS terms.” Warner-
Lambert Co. v. United States, 407 F.3d 1207, 1209 (Fed.
Cir. 2005). In so doing, however, “we accord deference to
a classification ruling by Customs to the extent of its
‘power to persuade.’” Link Snacks, Inc. v. United States,
742 F.3d 962, 965 (Fed. Cir. 2014) (quoting United States
v. Mead Corp., 533 U.S. 218, 235 (2001)). And in review-
ing a decision of the Court of International Trade, “we
give great weight to the informed opinion” of that court,
which has expertise in international trade matters, in-
cluding classification rulings. Schlumberger Tech. Corp.
v. United States, 845 F.3d 1158, 1162 (Fed. Cir. 2017).
    The classification of merchandise proceeds in two
steps. First, the court must ascertain the meaning of the
CHEMTALL, INC. v. UNITED STATES                           7


tariff term, which is a question of law that we review de
novo. Second, the court must determine whether the
merchandise in question fits within those terms, which is
an issue of fact that we review for clear error. Where, as
here, there is no dispute about the nature of the mer-
chandise, the two-step inquiry “collapses into a question
of law [that] we review de novo.” Lemans Corp. v. United
States, 660 F.3d 1311, 1315 (Fed. Cir. 2011).
                             B
     The HTSUS governs the classification of imported
merchandise and is “considered to be statutory provisions
of law for all purposes.” Schlumberger, 845 F.3d at 1163
(quoting 19 U.S.C. § 3004(c)(1)). The HTSUS is organized
by headings, which are represented by the first four digits
of an HTSUS provision. The headings are further divided
into subheadings. Id. at 1163 & n.4. The HTSUS also
contains General Notes, General Rules of Interpretation
(“GRI”), and chapter or section notes. Id. The section and
chapter notes “are not optional interpretive rules, but are
statutory text.” Park B. Smith, Ltd. v. United States, 347
F.3d 922, 926 (Fed. Cir. 2003); see also GRI 1 (“[F]or legal
purposes, classification shall be determined according to
the terms of the headings and any relative section or
chapter notes . . . .”).
    Applying GRI 1, a court “first construes the language
of the heading, and any section or chapter notes in ques-
tion, to determine whether the product at issue is classifi-
able under the heading.” Orlando Food Corp. v. United
States, 140 F.3d 1437, 1440 (Fed. Cir. 1998). After deter-
mining that the product is classifiable under the heading,
the court looks to the “subheadings to find the correct
classification for the merchandise.” Id. If an imported
article is “described in whole by a single classification
heading or subheading, then that single classification
applies, and the succeeding GRIs are inoperative.”
8                          CHEMTALL, INC. v. UNITED STATES




CamelBak Prods., LLC v. United States, 649 F.3d 1361,
1364 (Fed. Cir. 2011).
     When a tariff term is not defined in either the HTSUS
or its legislative history, the term is “construed according
to [its] common commercial meanings.” Millenium Lum-
ber Distribution Ltd. v. United States, 558 F.3d 1326,
1329 (Fed. Cir. 2009); see also Carl Zeiss, Inc. v. United
States, 195 F.3d 1375, 1379 (Fed. Cir. 1999) (“Absent
contrary legislative intent, HTSUS terms are to be con-
strued according to their common and commercial mean-
ings, which are presumed to be the same.”). “To discern
the common meaning of a tariff term, we may consult
dictionaries, scientific authorities, and other reliable
information sources.” Kahrs Int’l, Inc. v. United States,
713 F.3d 640, 644 (Fed. Cir. 2013).
    In addition, a court may consider the explanatory
notes published by the World Customs Organization. The
explanatory notes “provide persuasive guidance and ‘are
generally indicative of the proper interpretation,’ though
they do not constitute binding authority.” Schlumberger,
845 F.3d at 1164 (quoting Kahrs Int’l, 713 F.3d at 645).
                            III
    The parties agree that ATBS should be categorized
under HTSUS heading 2924, in the portion of that head-
ing that applies to acyclic amides and their derivatives.
That portion of heading 2924 contains three subheadings
at the six-digit level: two (subheadings 2924.11 and
2924.12) cover specific named compounds. The third
(subheading 2924.19) covers “Other” acyclic amides and
their derivatives. Because ATBS is not one of the named
compounds, the parties agree that it must fall under
subheading 2924.19. That subheading is further divided
into “Amides” (subheading 2924.19.11) and “Other” (sub-
heading 2924.19.80). If, as the Court of International
Trade held, ATBS is not an amide, it must fall under
subheading 2924.19.80. That disposition is required by
CHEMTALL, INC. v. UNITED STATES                               9


Subheading Note 1 to chapter 29 of the HTSUS, which
provides that, absent a specific contrary designation,
derivatives of a chemical compound are to be classified in
the residual “Other” subheading if there is one in the
series of subheadings at issue.
     As a preliminary matter, the parties disagree about
the meaning of the term “derivative” in HTSUS heading
2924. Chemtall argues that a “derivative” is limited to a
compound that is chemically derived from another com-
pound. The government argues that the term “deriva-
tive,” as used in the HTSUS, refers to compounds that are
related by structure, not solely by method of manufacture.
We agree with the government’s definition. See E.T. Horn
Co. v. United States, 367 F.3d 1326, 1332 (Fed. Cir. 2004)
(“‘[D]erivatives’ . . . should be given its broad, ‘structurally
related’ meaning.”); Webster’s Third New Int’l Dictionary
608 (1986) (defining “derivative” as “a chemical substance
that is so related structurally to another substance as to
be theoretically derivable from it even when not so ob-
tainable in practice”); Merriam-Webster’s Collegiate
Dictionary 342 (10th ed. 1986) (defining “derivative” as “a
chemical substance related structurally to another sub-
stance and theoretically derivable from it.”); 1 Customs
Headquarters Ruling Letter 085775, at 2 (Feb. 27, 1990)
(“[B]ased on the structure of the HTSUSA, the Chapter
notes and the Explanatory Notes, it is our interpretation
that a derivative of a compound results from the modifica-
tion of that compound by adding to the moiety or basic
structure of the compound without loss of that basic
structure.”).
   On appeal, Chemtall renews its argument that ATBS
qualifies as an amide because an amide may have radicals

    1  We refer to the 1986 editions of the two cited dic-
tionaries, as those are the closest editions before the 1989
enactment of the HTSUS. See Airflow Tech., Inc. v.
United States, 524 F.3d 1287, 1291 n.2 (Fed. Cir. 2008).
10                         CHEMTALL, INC. v. UNITED STATES




that contain “hydrogen, hydrocarbyl, or substituted
hydrocarbyl.” Chemtall defines “substituted hydrocarbyl”
as “a hydrocarbyl where one or more hydrogen (H) atoms
have been replaced with substituents containing heteroa-
toms.” A heteroatom, Chemtall explains, is an atom that
is not carbon or hydrogen; it can include nitrogen, sulfur,
and oxygen.
    The government argues that for a compound to be
considered an amide, the radicals attached to the nitrogen
atom in the compound’s amide functional group must be
either alkyl or aryl groups, which contain only hydrogen
and carbon atoms. 2 Since ATBS contains heteroatoms,
the government contends that it cannot be considered an
amide and must instead be considered an amide deriva-
tive, classifiable not in the subheading for “Amides”
(subheading 2924.19.11), but in the alternative subhead-
ing for “Other” (subheading 2924.19.80).



     2   See Wade, supra, at 125 (defining “alkyl group” as
the “group of atoms remaining after a hydrogen atom is
removed from an alkane,” and defining “alkane” as a
“hydrocarbon having only single bonds . . . general formu-
la: CnH2n+2”); Hawley’s Condensed Chemical Dictionary
(Richard J. Lewis, ed., 13th ed. 1997) (defining “alkyl” as
a “paraffinic hydrocarbon group which may be derived
from an alkane by dropping one hydrogen from the formu-
la. . . . Such groups are often represented in formulas by
the letter R and have the generic formula CnH2n+1,” id. at
34; and defining “aryl” as a hydrocarbon group “whose
molecules have the ring structure characteristic of ben-
zene, naphthalene, phenanthrene, anthracene and similar
molecules (i.e., either the 6-carbon ring of benzene or the
condensed 6-carbon rings of the other aromatic deriva-
tives). For example, an aryl group may be phenyl C6H5 or
naphthyl C10H6. Such groups are often represented in
formulas by ‘R,’” id. at 94.).
CHEMTALL, INC. v. UNITED STATES                            11


    For the reasons set forth below, we find that the sec-
ondary sources are nearly all contrary to Chemtall’s
position, the limited evidence that supports Chemtall’s
interpretation is unpersuasive, and the explanatory notes
to Chapter 2924 of the HTSUS do not support Chemtall’s
definition of amide. The court therefore holds that ATBS
was properly classified under HTSUS subheading
2924.19.80.
                              A
    Although Chemtall announces in its brief that “multi-
ple treatises” support its definition of “amide,” an exami-
nation of Chemtall’s cited secondary sources discloses that
Chemtall promises much more than it delivers.
    To support its definition, Chemtall points to two or-
ganic chemistry textbooks. The first is L.G. Wade, Jr.,
Organic Chemistry (8th ed. 2013). First, Chemtall asserts
that a section of the Wade text “lists penicillin as a typical
amide,” despite the fact that penicillin has sulfur in a
radical bonded to the nitrogen atom. Based on that
characterization, Chemtall argues that an amide may
contain sulfur or other heteroatoms—i.e., atoms other
than hydrogen and carbon.
    Chemtall, however, mischaracterizes Wade. On the
page that Chemtall cites, Wade notes that “[c]yclic amides
are called lactams,” and provides examples of cyclic
amides. Wade, supra, at 984. Penicillin is not discussed.
Later, in a section that discusses the bioreactivity of
lactams, Wade states that “β-Lactams are unusually
reactive amides,” and that “the β-lactam ring is found in
three important classes of antibiotics . . . . Penicillins
have a β-lactam ring infused to a five-membered ring
containing a sulfur atom.” Id. Wade thus describes
penicillin as containing a lactam ring combined with a
separate ring containing a sulfur atom, but does not
characterize penicillin as an amide (as opposed to an
amide derivative). See Peter Vollhardt & Neil Schore,
12                         CHEMTALL, INC. v. UNITED STATES




Organic Chemistry: Structure and Function 945 (6th ed.
2011) (describing penicillin as a “β-lactam derivative”).
    More importantly, Wade’s definition of the term “am-
ide” is squarely contrary to Chemtall’s position:
     An amide of the form R–CO–NH2 is called a pri-
     mary amide because there is only one carbon atom
     bonded to the amide nitrogen. An amide with an
     alkyl group on nitrogen (R–CO–NR') is called a
     secondary amide or an N-substituted amide. Am-
     ides with two alkyl groups on the amide nitrogen
     (R–CO–NR'2) are called tertiary amides or N,N-
     disubstituted amides.
Wade, supra, at 984. Wade’s definition of amide, which
refers only to alkyl groups as substitutes for the hydrogen
atoms bonded to the nitrogen atom, supports the govern-
ment’s position, not Chemtall’s.
    The second textbook on which Chemtall relies is Da-
vid J. Hart et al., Organic Chemistry: A Short Course
(13th ed. 2012). 3 The Hart textbook describes itself as a
“brief introduction to modern organic chemistry . . . writ-
ten for students who, for the most part, will not major in
chemistry.” Id. at xvi. In the section Chemtall cites, Hart
describes the basic structure of a primary amide—i.e.,
amides with the “general formula RCONH2”—and pro-


     3  Chemtall did not cite Hart in its motion for sum-
mary judgment before the Court of International Trade,
and it was not made part of the record. Nevertheless,
“[t]o discern the common meaning of a tariff term, we may
consult dictionaries, scientific authorities, and other
reliable information sources.” Kahrs Int’l, 713 F.3d at
644; see also Phillips v. AWH Corp., 415 F.3d 1303, 1322-
23 (Fed. Cir. 2013) (en banc). We have therefore consid-
ered Hart on appeal even though it was not presented to
the trial court.
CHEMTALL, INC. v. UNITED STATES                            13


vides a number of examples of primary amides. Id. at
313. 4
     In the sentence that Chemtall emphasizes, Hart char-
acterizes secondary and tertiary amides as compounds “in
which one or both of the hydrogens on the nitrogen atom
are replaced by organic groups, are described in the next
chapter.” Id. Chemtall argues that the phrase “replaced
by organic groups” is broad enough to encompass substi-
tuted hydrocarbyls. But the sentence on which Chemtall
focuses does not purport to provide a definition of amide,
and the examples of secondary or tertiary amides depicted
in Hart contain only hydrogen and carbon atoms attached
to the nitrogen atom in the amide functional group. See
id. at 343–44. Furthermore, other sections of Hart sug-
gest that the “R” radical is limited to hydrocarbyls. See
id. at 42 (“R is the general symbol for an alkyl group.”); id.
at 558 (defining “Amides” as “Carboxylic acid derivatives
in which the –OH group is replaced by –NH2, –NHR, or
NR2”); cf. id. at 328 (defining amines, where “Primary
amines have one organic group attached to the nitrogen,
secondary amines have two, and tertiary amines have
three,” and where the “R groups in these structures may
be alkyl or aryl”).
    None of the other secondary sources cited by the par-
ties support Chemtall’s broad definition of an amide.
Rather, the textbooks and dictionaries cited by the par-
ties, and most of the sources consulted by the court,
suggest that amides have only hydrogen or hydro-
carbyls—alkyl or aryl groups—bonded to the nitrogen of


    4  Although Chemtall criticizes the trial court and the
government for relying on introductory organic chemistry
textbooks, the Wade text on which Chemtall relies is an
introductory text, and the Hart text, which is designed for
non-chemistry majors, is the least sophisticated of any of
the secondary sources cited by the parties.
14                        CHEMTALL, INC. v. UNITED STATES




the amide functional group. See A. David Baker et al.,
Organic Chemistry 834 (2d ed. 2010) (defining “amide” as
a derivative of carboxylic acid containing –NR2, –NHR, or
–NH2, in which “R can be an alkyl or an aryl group”);
Loudon & Parise, supra, inside cover (depicting the struc-
ture of an amide and stating “R = alkyl, aryl, H”); Janice
Gorzynski Smith, Organic Chemistry, G-2 (4th ed. 2014)
(defining “amide” as “[a] compound having the general
structure RCONR'2, where R' = H or alkyl”); T.W. Graham
Solomons & Craig Fryhle, Organic Chemistry 72 (10th ed.
2011) (“Amides have the formulas RCONH2, RCONHR',
or RCONR'R'' where a carbonyl group is bonded to a
nitrogen atom bearing hydrogen and/or alkyl groups.”);
Andrew Streitwieser et al., Introduction to Organic Chem-
istry 551 (4th ed. 1992) (“Amides, RCONH2, are com-
pounds in which the hydroxyl group is replaced by an
amino group. The nitrogen of the amino group may bear
zero, one, or two alkyl groups.”); Wade, supra, at 984;
Amide, Chemistry-Dictionary, http://chemistry-dictionary
.com/definition/amide.php (an amide is a “[c]ompound
that can be considered a derivative of ammonia in which
one or more hydrogens are replaced by [] alkyl or aryl
groups”); Gamini Gunawardena, Amide, OChemPal,
http://www.ochempal.org/index.php/alphabetical/a-b/amide)
(“An amide is a carboxylic acid derivative [in which] R1,
R2 and R3 could be hydrogen atoms, alkyl groups, aryl
groups, or any combination thereof.”).
    To be sure, there are secondary sources—not cited by
the parties—that provide some support for Chemtall’s
definition. Jonathan Clayden et al., Organic Chemistry
(2d ed. 2012), refers to two examples of amides, aspar-
tame and paracetamol, each of which has heteroatoms in
the radicals that are bonded to the nitrogen atom. Id. at
31. Similarly, John McMurry, Organic Chemistry (9th ed.
2016), suggests that dipeptides, which also contain het-
eroatoms, are amides. Id. at 692. The cited passages in
Clayden and McMurry, however, are not definitional in
CHEMTALL, INC. v. UNITED STATES                         15


nature, and they may be understood as labeling com-
pounds as amides that other sources would describe as
amide derivatives, a distinction that is not always drawn
in the texts but is expressly recognized in the HTSUS
subheading classifying acyclic amides.
    In sum, the great weight of authority indicates that
amides, when precisely defined, are limited to having only
hydrogen, alkyl, or aryl groups bonded to the nitrogen
atom. Because ATBS contains sulfonic acid (SO3H) in a
radical attached to the nitrogen atom of the amide func-
tional group, ATBS cannot, under the definitions provided
in the secondary sources, be an amide.
                            B
    Chemtall relies heavily on the testimony of its expert,
Dr. Robson F. Storey, who took the position that ATBS is
an amide because an amide can contain a “substituted
hydrocarbyl” containing a heteroatom. Neither Dr. Sto-
rey’s testimony, nor the evidence on which he relied, is
persuasive, particularly in light of the broad consensus
among the treatises, dictionaries, and textbooks that
amides are limited to amide functional group compounds
in which hydrogen, alkyl, or aryl groups are bonded to the
nitrogen atom.
     Dr. Storey insisted that his definition is “recognized
universally by academic scientists,” but his only citation
to support that assertion was the Wade textbook, which,
as discussed above, is contrary to Dr. Storey’s definition.
The Court of International Trade considered Dr. Storey’s
definition but found that it is not supported in the scien-
tific literature, a finding in which we concur. 5 Moreover,

   5  The Court of Customs and Patent Appeals and the
Court of International Trade have held that expert wit-
ness opinions may be considered in determining the
meaning of a tariff provision, but that such opinions are
merely advisory, United States v. Crosse & Blackwell,
16                         CHEMTALL, INC. v. UNITED STATES




Dr. Storey’s definition of “amide” in his declaration is
undermined by the fact that his definition changed over
the course of this litigation. Before advocating for a
definition that includes substituted hydrocarbyls, Dr.
Storey stated in a 2011 declaration that an amide must
have “R1, R2, R3 [that] are independently hydrogen, alkyl,
or aryl,” which is the definition urged by the government
and adopted by the Court of International Trade. 6
     In support of his definition of “amide,” Dr. Storey re-
lied heavily on three patents: U.S. Patent Nos. 5,811,580
(“the ’580 patent”); 6,482,983 (“the ’983 patent”); and
8,383,760 (“the ’760 patent”). The ’580 patent is directed
to the preparation of “N-hydrocarbyl-substituted amides,”
’580 patent, col. 1, ll. 8–9, although the patent does not
provide a definition of the term “amide.” The ’983 patent
uses the phrase “N-hydrocarbyl substituted amides” only
in reference to the ’580 patent and other applications by
the same inventor as the ’580 patent. ’983 patent, col. 3,
ll. 26–28. Finally, the ’760 patent states: “As used herein,


Inc., 22 C.C.P.A. 214, 217–18 (1934), and “are given
weight only to the extent they are consistent with lexico-
graphic and other reliable sources,” Samsung Int’l, Inc. v.
United States, 887 F. Supp. 2d 1330, 1339 n.18 (Ct. Int’l
Trade 2012). See also Kahrs Int’l, Inc. v. United States,
791 F. Supp. 2d 1228, 1240 (Ct. Int’l Trade 2011) (expert
testimony as to the common meaning of terms “should be
subordinate to reliable textual sources”).
    6 Although in that declaration Dr. Storey also re-

ferred to ATBS as an “amide,” he did so on the ground
that ATBS is produced using a particular reaction, the
Ritter reaction, and that chemists “generally understand
that the product of the Ritter reaction is an amide.” He
also relied on the assertion that ATBS is similar to other
compounds that Customs classifies under subheading
2924.19.11.50. Chemtall has not pressed either of those
arguments on appeal.
CHEMTALL, INC. v. UNITED STATES                           17


‘amide’ refers to a compound of the following formula: [a
graphic depiction of an amide functional group] wherein
R1–R3 are each, independently, hydrogen or optionally
substituted hydrocarbyl.” ’760 patent, col. 5, ll. 8–18. Dr.
Storey is also a named inventor on a patent that defines
amides using the same definition as the ’760 patent. U.S.
Patent No. 8,344,073, col. 6, ll. 25–35.
    The cited patents do not support Chemtall’s conclu-
sion that the common and commercial meaning of amide
includes substituted hydrocarbyls. It is well recognized
that a patentee may set out a definition of a term and act
as his own lexicographer. See Thorner v. Sony Computer
Entm’t Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir. 2012).
The ’760 patent and Dr. Storey’s patent do so explicitly,
beginning the definition of “amide” with the phrase “[a]s
used herein.” As Dr. Storey testified, when questioned
about his own patent during his deposition: “The purpose
here was to cover compounds that were important to the
invention, not to put forth a definition of amide, necessari-
ly.” The patents cited by Dr. Storey thus do not contradict
the definition set forth in the cited dictionaries and other
secondary sources.
    Chemtall also relies on a government laboratory re-
port and testimony from the technician who prepared that
report. A Customs laboratory prepared a report on a
sample of ATBS, which identified it as “a carboxyamide-
function compound containing acrylamide and has char-
acteristics of 2-Acrylamid[o]-2-methylpropanesulfonic acid
(ATBS).” Chemtall points to three pages from the labora-
tory report that include test results and handwritten
comments written by the laboratory technician. The
handwritten notes read “consistent with secondary am-
ide” on one chart, “secondary amide N-H stretch” on a
second chart, and “Amide I C=O” and “Amide II N-H
Bend” on the third chart. The notes merely reflect the
laboratory technician’s recognition that ATBS contains an
amide functional group with one hydrogen atom bonded to
18                         CHEMTALL, INC. v. UNITED STATES




the nitrogen atom, indicating the general structure of a
secondary amide. And although the technician testified—
as a fact witness, not as an expert—that ATBS fell within
what he understood to be the definition of an amide, he
added that it was his understanding that any compound
containing an amide functional group would be considered
an amide. That very broad definition is inconsistent with
either party’s definition as well as being inconsistent with
the secondary sources cited above. The court does not
find the technician’s view as to the meaning of “amide” to
be a reliable indication of the common and commercial
usage of the term.
                             C
    The parties next debate the meaning of the explanato-
ry notes to heading 2924 as it relates to the interpretation
of the term “amide” as used in the tariff schedule. Each
side contends that the explanatory notes support its
argument. In fact, the explanatory notes contain internal
inconsistencies that render them of little use in discerning
the meaning of the term “amide” in the HTSUS.
    The explanatory notes first state that “[a]mides are
compounds which contain the following characteristic
groups”: (–CONH2), which the explanatory notes describe
as the basic structure of a primary amide; ((–CO)2NH),
which the explanatory notes describe as the basic struc-
ture of a secondary amide; and ((–CO)3N), which the
explanatory notes describe as the basic structure of a
tertiary amide. That description of “amide” means that a
secondary amide must contain two –CO groups, and a
tertiary amide must contain three such groups. To the
extent that description is taken as definitional, it is very
narrow and is at odds with the definition of “amide”
offered by either Chemtall or the government.
    Moreover, that description of “amide” is inconsistent
with the next sentence of the explanatory notes, which
states, “[t]he hydrogen of the (–NH2) or (>NH) groups may
CHEMTALL, INC. v. UNITED STATES                           19


be substituted by alkyl or aryl radicals, in which case the
products are N– substituted amides.” As the Court of
International Trade found, that sentence supports the
government’s position that an amide may include only
alkyl or aryl radicals. Chemtall argues that this sentence
does not foreclose the possibility that the hydrogen atom
may be substituted by other radicals as well, including a
“substituted hydrocarbyl” radical. That interpretation of
the “may be substituted” sentence is unconvincing. By
listing the groups that “may be substituted” for the hy-
drogen atom, the explanatory notes implicitly exclude
other groups. 7
    Other parts of the explanatory notes, however, appear
at least facially to be inconsistent with the limitation that
an amide may contain only alkyl or aryl radicals in the R2
and R3 radicals. For example, the next sentence of the
explanatory notes reads: “Some amides of this heading
also contain a diazotisable amine group.” A diazotisable
amine group includes an amine group, –NH2, bonded to
an aryl group, which would suggest that an amide can
contain, at the least, the heteroatom nitrogen in one of the
radicals bonded to the nitrogen in the amide functional
group. In addition, the explanatory notes provide exam-
ples of acyclic and cyclic amides that appear to be incon-
sistent, in part, with the explanatory notes’ definition of
amide. Although all of the acyclic amides feature only
hydrogen and hydrocarbyl groups bonded to the nitrogen


    7  Contrary to Chemtall’s argument, the word “may”
does not suggest that any number of other groups may be
substituted for the hydrogen atom. A statement in a
college catalog that “the required Organic Chemistry
course may be substituted by Physical Chemistry or
Inorganic Chemistry” would not be understood to suggest
that the student could also choose to substitute a course
in Thermodynamics for the required course in Organic
Chemistry.
20                          CHEMTALL, INC. v. UNITED STATES




atom of the amide functional group, some of the cyclic
amide examples contain atoms besides hydrogen and
carbon in the radicals that are bonded to the nitrogen
atom.
     Viewed as a whole, the explanatory notes do not clear-
ly weigh in favor of either party. On the one hand, the
definition that the “hydrogen . . . may be substituted by
alkyl or aryl radicals” is consistent with the definition
given in the dictionaries and textbooks cited above and
supports the government’s position. Similarly, although
the portion of the explanatory notes that describes prima-
ry, secondary, and tertiary amides as containing one, two,
or three –CO groups is inconsistent with the government’s
definition of amide, the more significant point is that it is
also inconsistent with Chemtall’s definition. That portion
of the explanatory notes, if adopted, would result in a very
narrow interpretation of the term amide that would
clearly exclude ATBS. 8
    On the other hand, the examples of cyclic amides that
include heteroatoms provide some support for Chemtall’s
definition of amide that allows “substituted hydrocarbyls.”

     8 The definition of amides as containing one, two, or
three –CO groups is not entirely without support. 1 Van
Nostrand’s Scientific Encyclopedia 182–83 (Glenn D.
Considine & Peter H. Kulik, eds., 10th ed. 2008), defines a
primary amide as an acyl radical (RCO–) linked to an
amido group (–NH2); a secondary amide as containing
“two acyl radicals and the imido group (=NH2)”; and a
tertiary amide as containing “three acyl radicals attached
to the N atom.” See also Int’l Union of Pure & Applied
Chemistry, Compendium of Chemical Terminology 69–70
(2014). That definition is consistent with the structural
formulas in the explanatory notes, although it is a much
more restrictive definition of the term amide than is found
in other texts, and it would exclude ATBS from being
considered an amide.
CHEMTALL, INC. v. UNITED STATES                         21


Even those examples, however, may be reconciled with
the explanatory notes’ definition of amide in light of the
structure of heading 2924 of the HTSUS. Unlike the
subheadings classifying acyclic amides, the subheadings
that concern cyclic amides do not draw a distinction
between “Amides” and “Other.” For that reason, it may
be that the drafters of the explanatory notes intended for
the listed examples of cyclic amides to represent the
entire class of cyclic amides and their derivatives, rather
than to draw a distinction between an “Amide” and an
“Other” compound, as is required for acyclic amides.
Accordingly, the examples of cyclic amides containing
heteroatoms may actually constitute amide derivatives,
which are not classified separately from cyclic amides
under the HTSUS.
     In any event, although the explanatory notes “provide
persuasive guidance” in interpreting the HTSUS,
Schlumberger, 845 F.3d at 1164, they are “not legally
binding and are to be consulted for guidance but not
treated as dispositive,” Carl Zeiss, 195 F.3d at 1378 n.1
(citing H.R. Rep. No. 100–576, 549 (1988)). The inconsist-
encies in the explanatory notes in this instance render the
notes of only limited assistance in interpreting the perti-
nent subheadings of the HTSUS. For the most part,
however, the explanatory notes either support the gov-
ernment’s definition of an amide or, at minimum, are
inconsistent with Chemtall’s definition. We therefore do
not find that the explanatory notes provide support for
Chemtall that would call for according the term “amide” a
broader definition than is suggested by the secondary
sources cited above.
                            IV
   Chemtall makes the alternative argument that if
ATBS is an amide derivative rather than an amide, it
should be classified under the ten-digit classification
22                         CHEMTALL, INC. v. UNITED STATES




2924.19.11.50 for “Other: Amides: Other.” That classifica-
tion would result in a 3.7% duty rate.
    In pressing its “tenth-digit” argument, Chemtall relies
on Subheading Note 1 to chapter 29 of the HTSUS. As
noted, the subheading note provides that derivatives of a
chemical compound are classified in the same subheading
as the compound unless they are more specifically covered
by another subheading, or there is a residual “other”
subheading in the same series of subheadings.
    Chemtall argues that, if ATBS is an amide derivative
rather than an amide, it must be considered a derivative
of acrylamide, which is assigned the statistical suffix
2924.19.11.10. Because the group of statistical suffixes
that includes acrylamide also includes the statistical
suffix 2924.19.11.50, which is denominated “Other,”
Chemtall contends that Subheading Note 1 requires that
ATBS must be classified under that ten-digit classifica-
tion.
     The first problem with Chemtall’s argument is that
the tenth-digit statistical suffixes, including the suffixes
for acrylamide and “other” amides, are not statutory. See
Pillowtex Corp. v. United States, 171 F.3d 1370, 1374
(Fed. Cir. 1999) (“[C]lassification of merchandise should
not be based upon the wording of statistical suffixes,
because statistical annotations, including statistical
suffixes, are not part of the legal text of the HTSUS.”);
Pima W., Inc. v. United States, 915 F. Supp. 399, 404 (Ct.
Int’l Trade 1996) (The statistical suffixes “are not includ-
ed among the appropriate references listed in GRI 1 and
in the legislative history of the HTSUS.”); HTSUS Statis-
tical Note 2 (The legal text of the tariff schedule does not
incorporate “statistical suffixes and any article descrip-
tions applicable thereto.”). The suffixes provide subdivi-
sions for statistical analysis purposes, but are not
intended to change the substantive tariff schedule.
CHEMTALL, INC. v. UNITED STATES                          23


     Moreover, Chemtall’s proposed application of Sub-
heading Note 1 would subvert the logical structure of the
first part of subheading 2924, which applies to “acyclic
amides (including acyclic carbamates) and their deriva-
tives [and] salts thereof.” Because it is agreed that ATBS
does not fall within subheadings 2924.11 or 2924.12, it
must fall within subheading 2924.19. The only two
statutory subheadings under subheading 2924.19 are
subheading 2924.19.11 (“Amides”) and subheading
2924.19.80 (“Other”). Because ATBS is not an amide, it
must be an amide derivative and thus classifiable under
subheading 2924.19.11.80. The four tenth-digit subhead-
ings under subheading 2924.19.11 (“Amides”) consist of
three specific amides and an “other” category; the four
categories are listed at subheadings 2924.19.11.10
through 2924.19.11.50. Because the four tenth-digit
categories all fall under subheading 2924.19.11 (“Am-
ides”), a non-amide such as ATBS cannot fall within that
subheading or any of its statistical suffixes, and thus
cannot be classified under the tenth-digit suffix
2924.19.11.50 as an “Amide—Other.”
    For the reasons discussed, the distinction drawn in
subheading 2924.19 at the eighth-digit level between
“Amides” (subheading 2924.19.11) and “Other” (subhead-
ing 2924.19.80) forecloses Chemtall’s argument that
ATBS, if considered an amide derivative, could still be
classified under subheading 2924.19.11 as an “Amide.”
As is clear from that subheading and the statistical
suffixes under that subheading, the residual “Other”
category in statistical suffix 2924.19.11.50 is reserved for
other amides not specifically listed in statistical suffixes
2924.19.11.10 through 2924.19.11.30. Because an amide
derivative, such as ATBS, is not an amide, it is properly
classified in subheading 2924.19.80.
                       AFFIRMED
