4-NITRO-5-METHYL-2-SULPHOBENZOIC ACID 
211 
I CH, II C=C\, 
^0 , ; CeH*/ ^0 
so, so. 
This tends to cast a doubt on the situation, as it negatives 
partly, at least, by its influence the positive results given by 
the ammonia derivatives in favor of the other view. 
Tautomeric change is not a suitable explanation, where the 
two bodies are so distinctly differentiated from one another, 
unless the mechanism of the reactions shows definitely how such 
change does^occur. No proof for any such mechanism has been 
produced. The discovery of the two crystalline forms of the 
symmetrical acid chloride may or may not have a bearing on the 
question. 
From a physical standpoint, the work on our acid confirms by 
analogy the work done by Femsen and his students upion this 
■class of bodies. 
SUMMARY. 
1. Two acid chlorides, the symmetrical with a melting point 
of 134°, the unsymmetrical with a melting point of 83°, have 
been prepared. These bodies were peculiar only in that they 
could be separated by fractional crystallization from solution, 
and that when pure, they did not tend in the least to form con- 
stant melting mixtures. Two crystalline forms of the symmetrical 
acid chloride were isolated, but their differences were not in- 
vestigated closely. 
2. The derivative obtained by the action of ammonia upon 
the symmetrical acid chloride was the ammonium salt of the 
imide. From this the imide itself was prepared by the action of 
dilute hydrochloric acid. The silver salt and the potassium salt 
of the imide also were made and analyzed. 
3. The derivative obtained by the action of ammonia on the 
unsymmetrical acid chloride was the ammonium salt of the 
cyan acid; no imide was found. The silver and potassium salts 
of the cyan acid also were made and analyzed. 
4. The derivatives obtained by the action of aniline on the 
symmetrical acid chloride were the symmetrical dianilide and 
the anil. 
5. The derivatives obtained by the action of aniline on the 
unsymmetrical acid chloride were the symmetrical dianilide and 
the unsymmetrical dianilide. 
