170 PROCEEDINGS OF THE AMERICAN ACADEMY 



We soon found that our yield was greatly increased and the excess 

 of bromine proportionately decreased if the bromine was added 

 rapidly. Later, when it was found that a low temperature was essen- 

 tial to the formation of mucochloric acid, the pyromucic acid and water 

 were cooled with ice until the bromine had all been added, but the 

 yield was not perceptibly affected. 



We have obtained the best results by the following method : Pyro- 

 mucic acid is suspended in ten times its weight of water contained 

 in a flask fitted with reverse cooler and drop-funnel. The calculated 

 amount of bromine is then rapidly added, cooling only so far as may 

 be necessary to avoid loss of bromine. After the bromine is all added, 

 the flask is heated, and the liquid kept boiling for ten or fifteen min- 

 utes. The solution may then be allowed to crystallize direct, although 

 we have usually evaporated it until the hydrobromic acid began to 

 volatilize in abundance before allowing it to cool. In either case the 

 crystals should be well washed with cold water and recrystallized from 

 boiling water. In this way we have found it easy to obtain 70 per 

 cent and over of the theoretical yield.* 



The acid recovered from the mother liquors is usually very dark 

 colored, and it cannot be purified by recrystallization from water 

 either with or without the addition of bone-black. We have found, 

 however, that such an acid may be obtained perfectly white by one or 

 two recrystallizations from dilute sulphuric acid (1 : 4). 



As to the properties of mucobromic acid, we can only confirm the 

 statements of Schmelz and Beilstein. It crystallizes ordinarily from 

 water in irregular leafy aggregates, from acid solutions or from cer- 

 tain other solvents in distinct rhombic plates. From a solution in 

 concentrated hydrobromic acid, we have frequently obtained it in 

 large compact crystals, with edges 10 to 12 mm. in length, but so 

 striated as to render measurement impossible. It is sparingly soluble 

 in cold water, very readily in hot water, in alcohol or in ether. In 

 benzol or carbonic disulphide, it is very sparingly soluble in the cold, 

 but dissolves quite readily on heating. Chloroform takes uji a little 

 when hot, most of which it deposits on cooling. In warm concen- 

 trated sul[)huric acid, it dissolves freely, and, if not too strongly heated, 

 crystallizes out on cooling or on dilution. It melts at 120-121°, and 

 at a higher temperature it distils in part unchanged. 



* Under conditions favorable to complete crystallization from tlie concen- 

 trated hydrobromic acid which forms Mie mother liquors, we have obtained 78 

 per cent. 



