176 
IOWA ACADEMY OP SCIENCE 
As has been shown by Remsen,® List and Stein/ and others, 
the ortho sulphobenzoic acids either substituted or unsuhsti- 
tuted, give two isomeric acid chlorides, while such isomers are 
not found in case the carboxylic and sulphonic acid groups are 
in the meta or para position with respect to one another. In 
this instance it was found that on treatment with phosphorous 
pentachloride, the three salts of the acids which had been iso- 
lated from one another behaved differently, one of the dibasic 
acids giving only one acid chloride, while the isomeric acid gave 
two acid chlorides. The tribasic acid gave two chlorides also, 
as would be expected from the theory. 
The original investigation of these acids was carried only far 
enough to establish their constitution. The analyses of the 
products covered a few salts of each, and the presence or ab- 
sence of the isomeric acid chlorides was confirmed by the prep- 
aration of the ammonia derivatives. None of the prodinjts were 
analyzed, their differentiation, being by means of their melting 
points and crystalline form. 
Later, Karslake and Huston® made derivatives of the 6-nitro- 
3-methyl-4-sulphobenzoic acid. They confirmed the presence of 
only one acid chloride not only directly, hut also through the 
appearance of a single series of derivatives including the amide, 
anilide, toluide, and diester, in which nothing was found that 
would indicate that the acid chloride as made could he other 
than a simple substance. The present work was undertaken to 
complete cur knowledge of the second of these three acids. 
In previous work by Karslake and Bond,® the 4-nitro-5-methyl- 
2- sulphobenzoic acid was obtained in the form of the neutral 
potassium salt as the first crop of crystals from the oxidized 
nitro-xylene sulphonic acid. Analyses of this salt were per- 
sistently low in potassium, as is shown by the reported. 20.96 
per cent potassium as against the calculated 23.21 per cent. 
Analyses of the barium, acid barium, and silver salts gave very 
close results, however, and the constitution of the acid was 
considered fixed in spite of the discrepancy in the values for the 
potassium salt. Since then it has been found that this first crop 
of crystals is usually contaminated with unoxidized 6-nitro-l, 3- 
dimethyl-4-sulphonic acid in the form of the potassium salt. 
'”'3Am7~Ch^. J., 30, 247, 1903. 
'‘Ber., 31, 1648,. 1898. 
M. Am. Chem. Soc., 31, 1057, 1909. 
<5Loc. cit. 
