552 Dr. Gregory on the Preparation of Alloxan. 



the liquid has become somewhat viscid, and this, along with 

 the presence of the crystalline deposit of alloxan, gives a pecu- 

 liar character to the effervescence toward the end of the ope- 

 ration. I commonly find that with 2| fluid ounces of nitric 

 acid the point above alluded to is reached when about 1200 

 grains of uric acid dried at 212° have been dissolved. It does 

 not answer to operate on a much larger scale ; it is better to 

 use several dishes at once, each containing 2- or at the most 

 3 fluid ounces of acid. For every 500 grains of uric acid 

 1 fluid ounce of nitric acid may be allowed. 



The whole is now allowed to stand all night in a cool place, 

 and next day the alloxan is collected on a funnel with the aid 

 of a little asbestus. The mother-liquid drains off, and the 

 last portions of it are cautiously displaced by ice-cold water, 

 till the droppings are found to have only a moderately strong 

 acid taste. The alloxan on the funnel, which is anhydrous, 

 is then digested with just as much water at 140° or 150° F. as 

 will dissolve it. The solution is filtered, and on cooling de- 

 posits a large crop of crystals of hydrated alloxan. [Should 

 too much water have been added, the filtered liquid must be 

 evaporated at from 120° to 140° F., till on cooling it crystal- 

 lizes abundantly.] The mother-liquid of these crystals, eva- 

 porated at the same temperature, yields a second crop. The 

 mother-liquor of this is added to the acid mother-liquor previ- 

 ously drained off, and the whole liquid treated, after the addi- 

 tion of two or three times its bulk of water, with sulphuretted 

 hydrogen, till the alloxan present is reduced to the state of 

 alloxantine. As a part is always reduced still further to dia- 

 luric acid, the liquid must be exposed to the air for a day or 

 two, or until it deposits no more crystals. The alloxantine is 

 purified by solution in boiling water, filtration to separate 

 sulphur, and crystallization ; and when dry three parts of it 

 correspond to rather more than four of hydrated alloxan. If 

 required, it may very easily be converted into alloxan; as 

 Schlieper has described this process I need not repeat it here. 



The mother-liquid of the alloxantine generally yields some 

 parabanic acid ; but very little if the process has been care- 

 fully performed. 



I think it will be admitted that the above process is suffi- 

 ciently simple. It will be observed that I no longer recom- 

 mend the separation of the alloxan formed from the nitric 

 acid in several successive portions, but that there is only one 

 operation for all, in which the alloxan is collected on a funnel 

 with asbestus. I used sometimes to divide the process into 

 five successive operations, and generally made three of them : 

 but I am now convinced that it is best to dissolve in the nitric 



