Dr. Gregory on the Preparation of Alloxan. 551 



never failed to obtain this as an average result since my pro- 

 cess was published, although I have very often repeated the 

 process. Several of my pupils have been equally successful. 

 I shall now, therefore, describe the process as I have for some 

 time pursued it, and its simplicity will, I trust, be evident. 



In my original account of this process, I recommended the 

 use of nitric acid of sp. gr. 1*3 to 1*35, and it was with such 

 acid, as I believed, that my results were obtained. But as 

 Schlieper found it impossible to succeed with acid of less 

 sp. gr. than 1*4 to 1*42, I suspect that I may have been mis- 

 taken as to the sp. gr. of my acid. This I cannot now ascer- 

 tain; but it is rendered probable by the circumstance that, in 

 the experiments about to be mentioned, I found an acid of 

 1*412 to answer my purpose perfectly, with the same appear- 

 ances as I had formerly observed. 



Schlieper having corrected this error proceeds to describe 

 my process, as performed by him, with great accuracy and 

 minuteness, and his description of the phaenomena entirely 

 agrees with my experience. J can only account for his not 

 obtaining such favourable results as I have always done, to the 

 circumstance of his acid being a little too concentrated. How- 

 ever this may be, on reading his paper I proceeded to repeat 

 my process, and obtained the results to be hereafter stated. 



The following is the process I now follow : — 2 or 1\ fluid 

 ounces of colourless nitric acid, sp. gr. 1*412, are placed in a 

 flat-bottomed dish or beaker glass, and as much uric acid is 

 introduced as will lie on the point of a small spatula. This is 

 well-stirred in to prevent the formation of lumps, and in a few 

 minutes effervescence commences, the liquid becomes slightly 

 warm, and the powder dissolves. More uric acid is now 

 added, taking care never to exceed a certain small quantity, 

 and not to allow the liquid to become warm beyond a certain 

 degree, which is easily judged of by laying the dish on the 

 hand. If too hot when uric acid is added, or if too much acid 

 be added at once, the uniform steady effervescence is changed 

 into a violent and tumultuous action, after which no alloxan 

 can be obtained. It is proper to have a plate with cold water 

 at hand, in which to place the dish or glass if it should seem 

 likely to become too warm. But a little practice enables us 

 to regulate the operation so that no external cooling is re- 

 quired. 



After several portions of uric acid have been added, crystals 

 of alloxan begin to appear in the warm liquid, but the addi- 

 tion of uric acid is to be continued, with the same precautions, 

 till so much alloxan has been formed, that on cooling the 

 whole becomes nearly semisolid. When this point is reached 



