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Guareschi, ibid, clxxi. 141.

Meyer and Stiiher, ibid clxv. 186.

Guareschi, Bnr- Deutsch. Chem. Go*, vii. 1462.



174 AROMATIC COMPOUNDS.

It is converted into aniline by the action of bromine in
alkaline solution, just as acetamide in similar circumstances
yields methylamine (p. 113).

Benzamide hydrochloride, C 6 H 5 .CO.NH 2 .C1H, is formed by
dissolving benzamide in hot concentrated hydrochloric acid, 1
or by passing hydrochloric acid into a mixture of equal mole-
cules of benzonitril and water. 2 It crystallizes in long prisms,
which rapidly lose acid in the air.

Mercuric benzamide, (C 6 H 5 .CO.NH) 2 Hg, is prepared by dis-
solving mercuric oxide in a hot, aqueous solution of benzamide ; 3
on cooling the liquid, a semi-solid crystalline mass is formed,
which is obtained by re-crystallization from alcohol in plates
melting at 222 224 . 4

2105 Benzoyl derivatives of amines and amido-bases are formed
by the action of benzoyl chloride on the latter :

Melting- Boiling-
point, point.
Dimethylbenzamide : 5

C 6 H 5 .CO.N(CH 3 ) 2 , large crystals . 41 42 255 257

Diethylbenzamide : 6

C 6 H 5 .CO.N(C 2 H 5 ) 2 , liquid .... 280 282

Ethylenebenzamide : 7

(C 6 H 5 .CO.NH) 2 C 2 H 4 , needles . . 249'

Benzanilide, or Benzoylaniline, C 6 H 5 .N(CO.C 6 H 5 )H. Gerhardt
obtained this compound by the action of benzoyl chloride on
aniline, 8 and Leuckart found that it is also formed when phenyl
isocyanate is treated with benzene in presence of aluminium
chloride. 9 It is insoluble in water and crystallizes from alcohol
in nacreous plates, which melt at 160 161 , 10 and volatilize
without decomposition at a higher temperature. It is not
attacked by boiling aqueous acids or alkalis, but yields aniline
and benzoic acid when it is fused with caustic potash. Concen-

Dessaignes, Ann. Chcm. Pharm. Ixxxii. 234.

Pinner and Klein, Bcr. Dcutsch. Chcm. Ges. x. 1896 ; xi. 10.

Dessaignes, loc. cit.

Oppenheim, Bcr. Deutsch. Chcm. Ges. vi. 1392.

Halhnann, ibid. ix. 846.

Ihid.

Hofmann, ibid. v. 246 ; Kraut and Schwartz, Ann. Chcm. Pharm. ccxxiii. 43

Ibid. Ix. 311 ; Ixxxvii. 164.

r ^ Dcwtsch - Chc - Ges. xviii. 873. '

Wallach and Hofmann, Ann. Chcm. Pharm. clxxxiv. 80.



BENZANILIDE. 175



trated nitric acid converts it into the three isomeric lenzoyl-
nitranilines, C 6 H 4 (NO 2 )N(CO.C 6 H 5 )H :

Melting-point.
Ortho, 1 long, light yellow needles . . 94 95

Meta, 2 plates 155'5

Para, 3 small prisms 199

The two latter are converted by reduction into the corre-
sponding benzoyldiamidobenzenes, C 6 H 4 (NH 2 )N(OO.C 6 H 5 )H,
while the ortho-compound forms phenylenebenzamidine,

/ NH \
C 6 H 5 .CK yC 6 H 4 , a substance which will be subsequently

described.

Molting point.

Benzoylmethylaniline : 5

C 6 H B N(CO.C 6 H 6 )CH 3 , small monoclinic crystals 59
Benzoyldiphenylamine : 6

(C 6 H 5 ) 2 N(CO.C 6 H 5 ), rhombic needles . . . 17G 177
Benzoylorthotoluide : 7

(C 6 H 4 .CH 3 )N(CO.C 6 H 5 )H, needles .... 142 143

Benzoylparatoluide : 8

(C 6 H 4 .CH 3 )N(CO.C 6 H 5 )H, long needles . . 155

2106 Methyknedibenzamide, CH 2 (NH,CO.C 6 H 5 ) 2 . By heating
hippuric acid, C 9 H 9 N0 3 (p. 181), with lead peroxide and dilute
sulphuric or nitric acid, Schwarz obtained a crystalline substance,
which he extracted from the product by alcohol. This dissolves
in concentrated sulphuric or nitric acid without change, and is
only attacked by oxidizing agents with difficulty and he therefore
called it hipparaffin (ITTTTO?, parum affinis). Its analysis led to
the formula C 16 H 16 N 2 O 2 . 9 Maier, who also prepared it, assigned
to it the composition C 8 H 7 NO, and found that another crystal-
line substance, hipparin, C 8 H 9 NO 2 , is obtained in its prepara-
tion. 10 Schwarz subsequently resumed his investigation, and
showed that the latter compound is ethyl hippurate ; by heating

1 Mears, Ber. Deutsch. Chcm. G<x. ix. 774 ; Schwarz, ibid. x. 1709.

2 Bell, ibid. vii. 498 ; Hiibner, ibid. x. 1716.

3 Stover, ibid. vii. 463 and 1314.

4 C. A. Bell, ibid. vii. 497 and 1504 ; Senncwald, ibid. ix. 775 ; Stover, loc. cit.

5 Hepp, ibid. x. 237.

6 Hofmann, Ann. Chem. Pharm. cxxxii. 166 ; Bernthsen, ibid, cxcii. 13.

7 Briickner, ibid. ccv. 230.

8 Kelbe, Ber. Deutsch. CJiem. ftcs. viii. 875.

9 Ann. Chem. Pharm. Ixxv. 201.
10 Ibid, cxxvii. 162.






AROMATIC COMPOUNDS.



hipparaffin with water to 170 180, he obtained benzamide
and a substance which gave the reactions of an aldehyde, and
which he identified, in spite of some differences in its properties,
with the ethylenedibenzimide which he had obtained by the
action of phosphorus pentoxide on a mixture of aldehyde and
benzamide. 1 Kraut and Schwarz, however, found thao it is
actually identical with methylenedibenzamide, 2 which had been
obtained by Hepp and Spiess by the action of concentrated
sulphuric acid on a mixture of methylal, CH 2 (OCH 3 ) 2 , and
benzonitril. 3

It is insoluble in cold, slightly soluble in hot water, and
crystallizes from alcohol in bushy aggregates of needles, melting
at 223. It is decomposed on boiling with 32 per cent, sulphuric
acid, with formation of ammonia, benzoic acid and formaldehyde.

Ethidenedibenzamide, CH 3 .CH(NH.COC 6 H 5 ) 2 . Limpricht
obtained this compound by the action of benzoyl chloride on
aldehyde-ammonia, 4 and Nencki by that of benzamide on alde-
hyde containing a few drops of hydrochloric acid. 5 It is prepared
by adding first paraldehyde and then benzonitril to well-cooled
sulphuric acid, and diluting with water after some hours (Hepp
and Spiess). It crystallizes from alcohol in long, white needles,
which melt at 204 and sublime without decomposition. It is
decomposed by fuming nitric acid into aldehyde and benzamide.

Dibenzamide, N(CO.C 6 H 5 ) 2 H, was prepared by Baumert and
Landolt, together with benzamide, by the action of benzoyl
chloride on potassium amide. 6 Earth and Senhofer found that
it is readily formed when benzonitril is treated with a mixture
of sulphuric acid and phosphorus pentoxide; the solution is
allowed to stand for some hours and then diluted with water,
which slowly precipitates the compound in crystals : 7

2C 6 H 5 .CN + 2H 2 O = (C 6 H 5 .CO) 2 NH + NH 8 .

It is also formed when lophine, which is obtained by the
dry distillation of hydrobenzamide, is treated with a solution
of chromium trioxide in acetic acid, it being thus smoothly
converted into benzamide and dibenzamide : 8

C 21 H 16 N 2 + 20 +H 2 = C 7 H 5 O.NH 2 + (C 7 H 5 0) 2 NH.

1 Wicn. Akad. Ber. Ixxvii. 762. 2 Ann. Chem. Pharm. ccxxiii. 40.

3 Ber. Deutsch. Chem. Gcs. ix. 1424. 4 Ann. Chcm. Pharm. xcix. 119.

Ber. Deutsch. Chem. Oes. vii. 159. Ann. Chem. Pharm. cxi. 5.

7 Ber, DeiOsch. Chem. Gcs. ix. 975, 1073. 8 E. Fischer and Proschke, ibid.

xiii. 708.



THIOBEXZAMIDE.



It separates from dilute alcohol in long, thin needles, which
melt at 148, and decompose at a higher temperature, giving off
an odour of benzaldehyde. It is almost insoluble in cold and
scarcely soluble in hot water, but dissolves readily in ether,
chloroform and benzene, from the last two of which it separates
in rhombic crystals. On boiling with caustic potash it decom-
poses into benzoic acid and ammonia.

It dissolves readily in dilute caustic soda, the solution when
concentrated depositing small glittering needles of the com-
pound (C 7 H 5 O) 2 NIs"a ; it also occurs in short, distorted prisms
containing half a molecule of water, which is evolved at 120.
The solution gives a precipitate with silver nitrate, consisting
of (C 7 H 5 O) NAg, and is also precipitated by other metallic salts.

Schafer, by heating benzamide in a stream of hydrochloric
acid, obtained a compound which he considered to be dibenz-
amide hydrate (C 7 H 5 O) 2 NH + 2H 2 O; it crystallizes in small
plates, -which melt at 99, and do not lose water at a higher
temperature, but decompose into benzoic acid and benz-
amide. 1 This substance is evidently acid ammonium benzoate,
C 7 H 5 (NH 4 )0 2 +C 7 H 6 2 . 2

Dibenzanilide, (C 6 H 5 .CO) ? NC 6 H 5 . Gerhardt and Chiozza ob-
tained this compound by the action of benzoyl chloride on benz-
anilide. It crystallizes from alcohol in fine, lustrous needles,
\vhich melt at 137 and sublime when more strongly heated. 3
By heating benzoic acid with phenyl mustard oil, Losanitsch
obtained a crystalline, foliaceous mass of a dibenzanilide, melt-
ing at 155". 4 Steiner, on the other hand, who prepared it by
Gerhardt's method and also by heating tribenzhydroxylamine,
N(OC 7 H 5 O)(C 7 H 5 O) 2 , found the melting-point of both prepara-
tions to be 16l. 5

Tkiobenzamidc, C 6 H 5 .CS.NH 2 , was prepared by Cahours by
passing sulphuretted hydrogen into an alcoholic, ammoniacal
solution of benzoiiitril :

C 6 H 5 ON + SH 2 = C 6 H 5 .CS.NH 2 .

It crystallizes from hot water in long, yellow needles, melting
at 117; when heated with water and mercuric oxide, it is recon-
verted into benzonitril, while it is reduced to benzylamine by

1 Ann. Chem. Pharm. clxix. 111.

2 Beilstein, Org Chem. 2nd Edition, ii. 747.

3 Ann. Chem. Pharm. Ixxxvii. 302.

4 Her. Deutsch. Chem. Gas. vi. 176.

5 Ann. Chem. Pharm. clxxviii. 235.

Vol.. in. PART IV. N



178 AROMATIC COMPOUNDS.



zinc and hydrochloric acid. 1 Iodine acts upon its alcoholic
solution in the following manner :

2C 7 H 7 SN + 2I 2 = C U H 10 SN 2 + 4HI + S.

The compound obtained in this way crystallizes from hot
alcohol in lustrous, snow-white needles, which melt at 90 and
distil without decomposition at a higher temperature. It is a
very stable compound, and is not altered by being heated to 150
with hydrochloric acid, sulphuric acid or tolerably concentrated
nitric acid. On boiling with caustic potash it is gradually con-
verted into ben zoic acid, ammonia being evolved. Zinc and
hydrochloric acid reduce it in alcoholic solution to the base,
C 14 H 14 N , 2 which is isomeric with ethenyldiphenylamidine
(Part III. p. 244) ; benzene and benzonitril are simultaneously
formed. 3 It crystallizes in small plates, melting at 71, is a
monacid base and forms an alkaline solution in alcohol.

Thiolenzanilide, or Phemjl/hiobenzamide, C 6 H 5 .CS.N(C 6 H 5 )H,
is formed when benzanilide is heated with phosphorus penta-
sulphide, 4 and crystallizes from alcohol in thin, yellow tablets or
prisms, melting at 97'5 98'5.

Diphcnylthiobenzamide, C 6 H 5 .CS.N(C 6 H 5 ) 2 , is formed when
asymmetric diphenylbenzenylamidine is heated to 130 140
with carbon disulphide :

C 6 H 5 .C(NH)N(C 6 H 5 ) 2 + CS 2 = C 6 H 5 .CS.N(C 6 H 5 ) 2 + CNSH.

It crystallizes from solution in benzene or alcohol in dark
yellow, asymmetric prisms, melting at 150 151. 5

2107 Benzoyl urea, C 6 H 5 .CO.NH.CO.NH 2 . Zinin obtained
this compound by heating urea to 150 155 with benzoyl
chloride ; 6 the anhydride may be substituted for the chloride in
this reaction. 7 The monobenzoyl urea crystallizes from alcohol in
long, thin plates, which melt atabout 200 and decompose into benz-
amide and cyanuric acid when carefully heated beyond this point.

( TVTT O IT

Symmetric ethylbenzoyl urea, 8 CO | ^H COG jj > needles.

Asymmetric ethyl- } r\n < NH

benzoyl urea/ j C ' { N(C 2 2 H 5 )CO.C e H 5 > rhombohedra '

Hofmann, Br,r. Dcutsch. Chem. Ges. i. 102. 2 Ibid. ii. 644.

Wanstrat, ibid. vi. 335. < Bernthsen, ibid. xi. 503.

Bernthsen, Ann. Chem. Pharm. cxcii. 37. 6 Ibid. xcii. 404.

Oeuther, Scheitz and Marsh, Zeitse.hr. Ch'm. 1868, 305.
Leuckart, Jonrn. PraJct, Chem. [2] xxi. 33 ; Miquel, Ann. Chim. Phys. [5]
318. 9 Lowner, Journ. Prnkt. Chem. [2] x. 2. r >l.



WIJKXZOYL UREA.



Dilcnzoyl urea, CO(NH.CO.C 6 H 5 ) 2> is formed, together with
hydrochloric acid, carbon dioxide, ammonium chloride, benzoic
acid and benzonitril, when benzamide is heated to 160 170
with carbonyl chloride, 1 and also from guanidine and benzoic
anhydride at 100V 2

NH,

I /CO.C 6 H 5 |

CurNH, + O< =NH,+CO



NH 2 NH.CO.C 6 H 5 .

It crystallizes from alcohol in needles melting at 210, and is
decomposed by boiling with strong acids into carbon dioxide,
ammonia and benzoic acid, while dilute caustic potash solution
converts it into benzamide and carbon dioxide.

Benzoyl thio-urea, C 6 H 5 .CO.NH.CS.NH 2 , is formed when thio-
urea is heated with benzoyl chloride 3 and by the action of dilute
ammonia on benzoyl thiocyanate.* It crystallizes from dilute
alcohol in small prisms which have a very bitter taste and melt
at 171.

JVliquel has prepared the following compounds by the action
of benzoyl thiocyanate on amines and amido-bases :

Melting-point.
Ethylbenzoyl thio-urea :



CS - e5 , fine prisms ..... 134

Phenylbenzoyl thio-urea :

CS { ^H C^ ' 115 ' long needles - 148 149
Benzylbenzoyl thio-urea :



Paratolylbenzoyl thio-urea :

sn - ' 165



Henzr.ylphenylhydrazinc, C 6 H 5 .NH-NH(CO.C 6 H 5 ). In order

to obtain this compound, two molecules of phenylhydrazine are
dissolved in five times their amount of ether, the solution cooled

1 Schmidt, Journ. Prakt. Chem. [2] v. 58.
- Creath, Ber. Deuixch. Chem. Get. vii. 1739.
9 Pike, ibid. vi. 755.
4 Miquel, Ann. Chim. Phy*. [5] xi. 313.



180 AROMATIC COMPOUNDS.

and then treated with a molecule of benzoyl chloride. The
mixture is filtered, the hydrochloride of phenylhydrazine removed
by boiling with water, and the residual benzoylphenylhydrazine
crystallized from boiling alcohol. It forms fine prisms, melting
at 168, dissolves readily in warm, dilute caustic potash, and
is precipitated from this solution by acids. Yellow mercuric
oxide converts it in alcoholic solution into lenzoylnzobenzenc,
C 6 H 5 .N=N.CO.C C H 5 , a dark red, oily liquid, which is reconverted
into the original compound by reduction. 1

Methylbenzoylphenylhydrazine, C 6 H 5 N(CH 3 ).NHi'CO.C 6 H 5 ).
This compound is prepared by adding sodium and then methyl
iodide to a solution of benzoylhydrazirie in wood-spirit; the
mixture becomes warm, and after standing for several hours is
heated to 100 for a short time in order to complete the reaction.
Methylbenzoylphenylhydrazine crystallizes from hot alcohol in
fine, white needles, melting at 153. When its solution in
hydrochloric acid is treated with a trace of nitrous acid, an
intense red colouration is produced, which becomes dark brown
with large quantities. When methylbenzoylphenylhydrazine is
heated with concentrated hydrochloric acid, it is decomposed into
benzoic acid and methylphenylhydrazine ; the latter compound
may be detected by conversion into its characteristic tetrazone,
which melts at 137, and not, as was formerly stated, at 133
(Part III. p.337)). 2

Dibenzoylphenylhydrazine, C 6 H 5 N(CO.C 6 H 5 )N(CO.C 6 H 5 )H, is
obtained by the action of benzoyl chloride on benzoylphenyl-
hydrazine or on potassium phenylhydrazinesulphonate. It crystal-
lizes from hot alcohol in fine prisms, which melt at 1 77 178,
and dissolve slowly in aqueous alkalis. If the alkaline solution
be treated with the calculated quantity of sodium and heated, the
sodium dissolves and on cooling, a salt, C 20 H 15 N 2 O 2 Na, separates
out in lustrous plates, which are readily soluble in water.

Methylr/ibenzoytphenylhydrazine, C (i H 5 N(CO.C 6 H 5 ) N(CO.C 6 H 5 )
CH 3 , is formed when the solution of the sodium salt is heated
with methyl iodide. It forms well-developed, soft, white crystals
which melt at 145, and are insoluble in water or alkalis, but
dissolve readily in hot alcohol. On distillation with caustic
potash it is decomposed into benzoic acid and hydrazophenyl-
methyl, C 6 H 5 .NH-NH(CH 3 ). This substance is a colourless oil
which rapidly oxidizes in the air, but forms stable salts. WTien

* E. Fischer, Ann. Clum. Pharm. cxc. 125.
" Tafel, Rer. Dcwtsch. Cliem. Ges. xviii. 1739.



HIPPUKIC ACID. 181



mercuric oxide is added to its ethereal solution, it is converted
into azophenylmethyl, C 6 H 5 N NCH 3 , a yellow oil, which pos-
sesses a characteristic smell, volatilizes with ether vapour, more
rapidly with steam, and distils at about 150 with considerable
decomposition (Tafel).

Benzoyldiphenylhydrazim,(VJl^ - NH(CO.C 6 H 5 ), was ob-
tained by Fischer from benzoyl chloride and diphenylhydrazine ;
it is slightly soluble in alcohol and ether, and crystallizes from
hot acetone in fine needles, melting at 192 . 1



HIPPURIC ACID, C 9 H 9 NO. V

2108 Rouelle, in the year 1776, as has been already mentioned
under benzoic acid, found a salt in the urine of the cow and the
camel, which is analogous to flowers of benzoin, and Fourcroy
and Vauquelin observed a peculiar acid, which they took to be
benzoic acid, in the urine of graminivora. Liebig, however,
showed in 1829, that this acid contains nitrogen and differs
completely from benzoic acid in its properties ; he says, ' Since
I have more especially investigated the acid obtained from the
urine of the horse, I will designate it, for want of a more suit-
able term, as " hippuric acid " (ITTTTO?, horse, ovpov, urine). On
heating it decomposes with formation of various products, among
them being benzoic acid, the experience of Fourcroy and
Vauquelin, " that benzoic acid can be obtained from horse's
urine, but is not contained in it as such " being thus confirmed.' 2
Liebig first obtained for it the formula C 10 H 10 NO 3 , which he
subsequently corrected, 3 his later analyses being confirmed by
those of Dumas and Peligot. 4 Pelouze then found that on
boiling hippuric acid with manganese dioxide and very dilute
sulphuric acid, benzoic acid, ammonia and carbon dioxide are
formed, 5 while Fehling obtained benzamide and carbon dioxide
by boiling it with water and lead dioxide. Dessaignes then made
the important observation that it is decomposed into benzoic
acid and glycocoll (amido-acetic acid) when treated with boiling
alkalis or acids, 7 and he, with the majority of chemists,



' Ann. Chan. /'/<,/. <:.\c. 78. - Pogy. Ann. xvii. 389.

:! ////'/. xxxii. :,~:\. * Ann. Chem. Pharm. xiv. 69.

6 Ibid. xxvi. 60. c Ibid, xxviii. 40.

7 Juitrn. Prakt. Chem. xxxvii. 244.



182 AROMATIC COMPOUNDS.

assumed that hippuric acid is a copulated compound of benzoic
acid and glycocoll, although, as was pointed out by Berzelius,
this assumption does not in the least account for the action of
lead dioxide.

An important advance towards the determination of the consti-
tution of hippuric acid was made by Strecker, 1 who found that it is
converted by the action of nitrous acid into benzoylglycollic acid
(p. 165), which was more closely investigated by him in conjunc-
tion with Sokolow. This compound assumes the elements of
water and splits up into benzoic acid and glycollic acid, and must,
therefore, be considered as a copulated compound of these, its
amido-derivative being hippuric acid. 2

Dessaignes now endeavoured to prepare hippuric acid arti-
ficially by heating glycocoll with benzoyl chlori.le, but without
success ; he attributed his failure to the evolution of hydrochloric
acid and therefore substituted the zinc salt of glycocoll, zinc
amido-acetate, and found that hippuric acid is slowly formed
when benzoyl chloride is allowed to act upon this in the cold,
more rapidly at 1 20. 3 He also obtained it subsequently by heat-
ing benzoic acid with glycocoll to 160, 4 and Jazukowitzsch pre-
pared it by heating chloracetic acid with benzamide ; 5 the yield
was, however, small, owing to the formation of free hydrochloric
acid. These syntheses finally proved that hippuric acid is
benzoylamido-acetic acid :

CH 2 .NH 2 CH,.NH.CO.C 6 H 5

+ HO.CO.C 6 H 5 = | +H,0.

COOH CO.OH

CH,C1 CH 2 .NH.CO.C 6 H r

| ' + NH 2 .CO.C 6 H 5 = | ' +HC1.

CO.OH CO.OH

It is also formed, together with other products which will be
subsequently mentioned, from benzoyl chloride and silver amido-
acetate, 6 and very readily when glycocoll is heated with benzoic
anhydride 7 or when benzoyl chloride is added to a concentrated
aqueous solution of the former. 8

Liebig detected it in human urine, about 1 grm. being excreted

1 Ann. Chcm. Pharm. Ixviii. 54. Ibid. Ixxx'. 17.

3 Ibid. Ixxxvii. 325. Jahresber. Chcm. 1857, 367.

8 Zeitschr. Chem. 1867, 466.

" Journ Prakt. Chem. [2] xxiv. 239 ; xxvi. 145.

7 Cuitius, Bar. Deutuch. Chem. Ges. xvii. 1662.

8 Baum, Zeitschr. Physiolog. Cliem. ix. 465.



HIPPURIC ACID. 183



per diem. 1 According to Weismann it is formed more freely during
a vegetable than an animal diet, 2 and according to Ducheck
it is not invariably present. 3 Pettenkofer found 1'3 per cent, of
it in the urine of a girl suffering from St. Vitus's dance, whose
diet consisted exclusively of apples and bread ; the amount
decreased as soon as meat was again taken. 4

Lehmann observed its occurrence during diabetes, even before
Liebig had detected its presence in normal human urine, 5 and
since that time it has frequently been observed in large
quantities in diabetic urine. It also occurs largely in the acid
urine of persons suffering from fevers of every kind. 6

Liebig, 7 and Dumas 8 assumed that fresh horses' urine contains
hippuric acid which is converted into benzoic acid on standing.
The former subsequently stated that horses and bullocks excrete
hippuric acid when they are allowed to remain idle for some
time, and benzoic acid when they are working to the full extent
of their powers, 9 and Erdmann and Marchand found 10 that the
urine of carriage horses usually contains the former and that of
plough horses the latter. Lehmann, however, who investigated
the urine of a large number of horses, both sound and diseased,
well and badly fed, found only hippuric acid without exception,
provided that the urine had not been allowed to stand too long
in the air. After standing for a considerable time, and especially
after the formation of ammonia, only benzoic acid is present,
being formed by a special ferment. When such urine was added
to a sample of the fresh material, containing hippuric acid alone,
the latter decomposed on evaporation and only benzoic acid could
then be detected. 11 Roussin found a large quantity of urea but
no hippuric acid in the urine of Arab stallions, which did not
work but were kept for breeding ; that of others, which were used
by the Spahis for riding, contained little urea, but O'o 1 per
cent, of hippuric acid ; in one sample of urine which was passed
after a long journey the amount rose to 1'4 per cent., and 0/78
per cent, was found in that of omnibus horses. 12

Stadeler found about 1'5 per cent, of hippuric acid in cows'

1 Baum, Zeitschr. Physiolog. Chem. cvi. 164.

2 Jahresber. Chem. 1858, 572. ' Gmelin, Org. Chem. v. 332.

4 Ann. Chem. Pharm. lii. 86. 5 Journ. Prdkt. Chem. vi. 113.

" Gmelin's Org. Chem. v, 334. 7 Ann. Chem. Pharm. xxx. 280.

8 Ann. Chim. Pints. Jvii. 331.

9 Ann. Chem. Pharm. xli. 272 ; Organ. Chem. in Anwendung auf Phys.
und Pathol. Ixxxiv.

10 Journ. Prnkt. Chem. xxvi. 491. n Gmelin. Organ. Cham. v. 3H2.

ij I'ornpt. rend. xlii. 583.



184 AROMATIC COMPOUNDS.

urine, 1 and, according to Hallwachs, a cow passes more than
50 grins, of the acid during twenty-four hours. 2 Kraut observed
that cows which are allowed to graze give more hippuric acid
than those which are stall fed, 3 while only traces are formed
when they are fed on spent grain from a distillery. 4

In the urine of cows fed on oat-straw and wheat-straw, with
the addition of some beans, 21 27 per cent, was found, while
that of cattle fed on bean-straw and clover contained only 0'4 per
cent., and when ordinary meadow hay was given, 14 per cent. 5
The urine of sucking calves contains uric acid but no hippuric
acid (Wohler). The latter occurs in the urine of sheep, goats,
hares, rabbits, and elephants (Schwarz). Schwarz found it in
very considerable quantity in the urine of a camel, the sample
being very concentrated, as only four ounces were passed during
the day, and Lehmann detected it in the urine of the tortoise
(Testudo graeca). Pettenkofer observed its occurrence in the
scurf which is formed on the skin during the rare disease known
as ichthiosis, 6 and J. Davy found it in butterflies, moths, and
their chrysalides and excrements. 7

The urine of dogs also contains a small quantity of the acid
even during an exclusively meat diet or after long fasting, 8
while it has never been found in the urine of pigs. 9

2109 Ure was the first to make the important observation
that the urine of a patient who has taken benzoic acid contains
a large amount of hippuric acid. 10 Wohler had previously
suggested that benzoic acid is changed to hippuric acid in the
organism, for he had found in the urine of a dog to which half a
drachm of benzoic acid had been given an acid which he mistook



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