OP ARTS AND SCIENCES. 205 



ing, it seemed to me worth while to attempt its preparation, more 

 especially in order to study the dichloracrylic acid derived from it, 

 and to compare this with the acid of the same composition which 

 "Wallach * had already made from chloralid. This investigation Mr. 

 W. Z. Bennett undertook with me. 



The method followed by Schmelz and Beilstein in making mnco- 

 chloric acid was as follows : Pyromucic acid suspended in water was 

 treated with chlorine at first in the cold and afterwards at boiling 

 heat. When all action appeared to be over, the solution was some- 

 what concentrated on the water bath, and finally brought to crystal- 

 lization by evaporation over sulphuric acid in vacuo. This method 

 gave in our hands precisely the same discouraging quantitative results 

 that Schmelz and Beilstein had obtained ; and it was only after a long 

 series of unsuccessful experiments that we succeeded in finding a 

 simple modification of the method which enabled us to prepare mate- 

 rial sufficient for investigation. We suspended the pyromucic acid in 

 ten times its weight of water, cooled the whole well with ice, and 

 passed in a rapid stream of chlorine until the liquid was thoroughly 

 saturated. The temperature was carefully kept within a few degrees 

 of the freezing point during this treatment with chlorine, and not 

 unfrequently considerable quantities of the crystalline hydrate of chlo- 

 rine separated. When the solution was saturated it was heated to 

 boiling, after a few moments again cooled to 0°, and saturated once 

 more with chlorine. When this operation had been repeated several 

 times, crystals of mucochloric acid began to appear as the solution 

 cooled. At first we filtered these crystals off", and subjected the fil- 

 trate to further treatment; but we found by experience that little 

 or no product was gained after the sixth ohlorination, and we, there- 

 fore, usually proceeded to this point before we removed the acid 

 formed. We then collected the crystals which separated as the 

 solution cooled, and evaporated the mother liquors on the water bath 

 to the point of crystallization. The crystals were drained, pressed, 

 and recrystallized from hot water. We further found it convenient 

 to add to the pyromucic acid a small percentage of iodine. Although 

 this was by no means essential, we found that our results were then 

 more constant and the average yield greater. As the result of 

 several preparations which we made in the course of the investiga- 

 tion, we obtained 129 grm. of mucochloric acid from 202 grm. of 

 pyromucic acid. This corresponds to a little more than forty per 



* Berichte der deutsch. chem. Gesellsch., viii. 1580. 



