I ) ( % ot)avrvctl i n c.r:cporation of the aolr e n t and drying, The temperaturo should not exceed 35" C., as thc compounds decompose a t higher temperatures or on prolonged exposure to air. This is especially true of nitroglycerin and pentaeryt'hritol tetranitrate. Amyl nitrite is volatile and care must be taken to avoid loss on prolonged heating or exposure to air. Addition of glac-ial acetic acid to the nitro compound residue after extraction seenis to stabilize the compound and solubilizes it for inow rapid color development. Attempts to confirm tlie totnl nitrogcn contcnt directly on rxtractcd material by the micro-Dumas nicthod were unsuccessful, yielding low nitrogen valLICS which indicated that considerable nitrogen was lost betir-een the time it. was extracted and the time the Dumas dcterminations were made. All microDumas determinations were run on the sugar-nitro compound mixtures. This reaction seems to be specific for the pharmacologically active -OXO, group, since nitromethane, nitrobenzene, nitrotoluene, and nitrourea gave no color. The reproducibility of the method with innnnitol hexaiiitrate in lactose alone and in cornprcasc3d tahlcts in cornbination with rauwolfia, rutin, and bes-
Iciiiovod froiri the sugar Iiy solrrmt e l Table 111. Reproducibility of Colorimetric Determination o f Mannitol Hexanitrate
M g . er Tablet
rc in
Bound (Calcd. 16 M g . pcr Tablet)
1,actose 7 09 7.12 7 11 7 08
16 1
7.11 7.14 7.10
ktction before color drvclopment. In spite of thc preliminary solvent estrartion necessary in this method, it is considerably less time-consuming than the degradation-distillation methods. Rrsults are rrproducible and well within the usual limitations of colorimetric methods. For these reasons the method lends itself we11 t o pharmaceutical control laboratory work.
16.1
15.8
15 9 16.2
7.10 7.09
lt5 8
7.12 Average 7 . I O St,d.dev. 0 . 0 178
lG.O
I d , 97 0.141
LITERATURE CITED
(1) British
Pharmacopoeia, 1932, 7th Addendum, p. 46, Constable &! Co., 10 Orange St., Lricester Square, 1,ondon \VCL%, 1943. (2) Cannon, J. H., Heurman, R. F., J .
ilssoc. O j i c . 4 g r . Chemists 34, 717 11951). (3) Desbassins de Richemont, Chem. Zenlr. 1835, 782. \
peridin is shown in Talile 111. Siinilar results were obtained with the other nitro conipounds. A number of medicinal agents commonly used in conjunction with these nitro compounds in therapy apparently do not interfere in determinations n i t h this method. These include rauwolfia, reserpine, phenobarbital, sodium pentobarbital, rutin, hesperidin, and theopliyllin. In a11 c a s ~ sthe nitro compound was
,
(4) Fcligl, Fritz, "Spot Tests," Vol. I, 4th ed., I).299, Elsevier, New York,
1954.
(5) Sarnoff, Evelyn, J . Sssoc. Ofic. Agr.
Chemzsts 38, 637 (1955); 39, 63
(1956).
( 6 ) Swann, M. H., Adams, M. L.. ANAL. CHEM.28, 1630 (1956). (7) U. S. Pharmacopoeia, 14th Revision, p. 331, Mack Publishing Co., Easton, Pa., 1950.
REFLIVED for review August 29, 1957. .icceytcd February 21, 1958
An a lysis of Am ino- Fo rma Ide hy de Resins JOSEPH
C. MORATH and JOHN T. WOODS
Organic Chemicals Division, American Cyanamid Co., Bound Brook, N. J. F M e t h o d s f o r analysis o f textile resins of the amino-formaldehyde t y p e a r e reviewed and summarized and, in some instances, a r e given in detail. Methods a r e included for the amino portion of the resin and the various forms o f formaldehyde and/or methanol. The chromotroDic acid method for total formaldehyde should b e of particular interest because of its speed and simplicity.
0
0
I
I1
H&C?jHCH,OH l\lononiethylol urea
CH,NHCSI CHzOH 'I
0 Ilimethylol urea (chain dimer) Dimethylo1 urpa
T
varii4y of rel-iiii of tlic uiiiiiio-foriiialtIfli?-dc type wet1 iii tlw tcstilc intlustrj. are constantly groning. Those most, romnionly used are formed b y the condensation of formaldehyde with melamine, urea, ethylene urea, or thiourea. They may be sirnplc condensations or cocondensstions of tn-o or more amino-type resins. liesins m a j ~also he rnetliylatcd or utimetliylated. The following structures illustrate a fen of the forms in which uiea-formaltleli!-de resins may exist.
Ii
HC)CHJTHCNCH,OH
111,;S L X I ~ L I { : i i i t l
0 11
SH-C-S-CH~OH I
I
CHZ
I €I()CII:---S---C---s
CH2 I1
~i
0
Dimethylol urea (ring dimer)
As the ~ i u m b e r and complexity of these resins grow! the need for analytical methods grows ako, to gire information on simple resins as \yell :ih niisturcs of rwirih.. This paptsr w i i i i i a r i ~ r bthe, i i u n i e r o i ~ ~ rnetliod~,iciittc,recl throughout the litcrature. for tlie determination of the aniino or formaldehyde portions of the resins, and in some cases proposes modifications. The following resin components are discussed. Amine Formaldehyde Methanol Cres Total Total 1:thylenrI U I N I'rcle Free llelnmine Methylol Thiourea XIethylated Methylenic VOL. 30, NO. 8, AUGUST 1958
1437
makes bpectrophotometrir determination possible. The data in Table I1 compare values for thiourea obtained by the ultraviolet method with calculated values.
Table I. Melamine Determination by Kjeldahl and Ultraviolet Methods
Resin
Kjeldahl
1
ti3 4, 63, 3
2
53.8, 53.4
:i
41.7,41 ti
DETERMINATION
OF
68 8. 60 4. 61 7 5 2 . 3 152.0, 52.3 -1I . n,41'. 8
AMINE
The Kjeltlahl method for nitrogen i i most commonly used for the determination of the amine portion of the resin; it normally gives reliable results, but is not always suitable. For mixturrs of amino-type reqins or for resins containing other nitrogenous matter, t h r Kjeldahl method does not differentiate bet15 ern the various nitrogen-containing components. Urea. An alternative method for t h e determination of urea is a refinement of Kappelmeier's method, described by Grad and Dunn ( 9 ) ; it involves refluxing the resin in benzylamine to form dibenzyl urea. Upon acidification the dibenzyl urea is precipitated, filtered, washed free of acid, dried, and weighed, and its urea equivalent ic: calculated. The main disadvantage of the method is the length of time necesPary for the refluv stepabout 8 hours. Ethylene Urea. T h e benzylamine method of Grad and Dunn (9) is also applicable to ethylene urra. As u4th urea resins, dibenzyl urea is formed. Although this method is not suitable for mixtures of urea and ethylene urea resins, it is applicable to either in the presence of other nitrogenous compounds. Melamine. 1Ielamine may be dcterniined by ultraviolet absoi ption measurement after refluxing for 1 hour in 0.1S hydrochloric acid ( I O ) . The absorbance is measured a t 237 mp, where melamine and ammeline have an isosbcstic point, instead of a t 235 nip, the absorption m:i\imum of melaminr. to corrrct for a small amount of ammcliiic formed during the hydrolj High \ v h r 5 :ire olitainrd I\ ith melamine rchin sirups, pro11:~hIyl~ecausc,of incomplctc liydroly4s of t h r resin. TTltraviolet curvrs of the unliyclrol~-zcd resin dion. that it ahsurliq niorc strongly than melamine in the region I\ here inclaniine absorbnc~:ilt~ulatctl 1)y c~i~rrrcting for tlic artual watw content of the original xainple tlct~criiiincrl1 ) ) ~ tlw lon-tcnipcraturc Karl F i d w iiictliod. The actual water content of the sample is determined at -40" C. in dimethylformamide instead of methanol to prevent intrrfcrence (methylation) of the niet,hylol groups during the analysis. Methylo1 formaldehyde is then calc~ulatctlfrom th(, water of rcwtioli. 11L'l'l: 1131l S . \ T I ( JX
IF
\\'.1'1.1,:11.
VOL. 30, NO. 8, AUGUST 1958
l
