4-NITRO-5-METHYL-2-SULPHOBENZOIC ACID 
179 
94°. The acid was titrated with sodium, hydroxide, using phe- 
nolphthalein as the indicator. 
.1916 g. acid gave .0330 H 2 O and required 5.60 cc .1088N HCl for its 
neutralization in the Kjeldahl process. 
.2057 g. acid required 11.90 cc. .1088N NaOH for direct neutraliza- 
tion. 
Theory for CsHANS.3H20 
Water, 17.14 per cent. 
Acid hydrogen, .635 per cent. 
Nitrogen, 4.44 per cent. 
Found 
17.22 per cent. 
.626 per cent. 
4.45 per cent. 
The Acid Chlorides. 
When the potassium salt of the 4-nitro-5-methyl-2-sulphoben- 
zoic acid is heated with phosphorous pentachloride, it is con- 
verted into the acid chloride. The product is not a simple sub- 
stance. On crystallizing from carbon tetrachloride, it gives two 
characteristically different crystalline forms which have the same 
composition, but which differ materially in respect to their be- 
havior with certain reagents such as ammonia, aniline, etc. The 
appearance of these isomeric chlorides is characteristic of the 
ortho acids either of the ortho dicarboxylic or ortho sulpho- 
benzoic type. It is among the latter especially that the problem 
has been worked upon,^ since the dicarboxylic acids, e. g., ortho 
phthalic acids, have a tendency to form a large excess of one 
isomer and very little of the other. 
The original argument regarding the constitution of these 
acid chlorides was based probably on the work done by Auger® 
on the chlorides of the dibasic acids. He found that if succinyl 
chloride was treated with ammonia, it gave a different diamine 
than when the ester of succinic acid was acted upon, and, since 
the latter could not have a symmetrical formula (I), he as- 
signed to the isomeric body the formula (II). The ease with 
which the symmetrical diamine goes over into the imine (III) 
is comparable with that of the formation of the acid anhydride, 
and forms part of the •argument. 
I 
CHg— CONH2 
CHg— CONH, 
II 
NH, 
CHs— 0— NHs 
I 
I / ^ 
CHs— C=0 
III 
CHs— 0 = 0 
I >™ 
OH,— 0=0 
'^Remsen and Students, Am, Chem. J,, 30, 247, 1903. 
sAuger. Bl. 39, 346, 1888. 
