46 Proceedings of the British Association. 



whole is then agitated with a wooden stirrer and kept heated. 

 Nitric acid is thus evolved in considerable quantity and purity, 

 from a large surface, and in such a manner that all the acid evol- 

 ved must necessarily pass through the melted wax. This method 

 answers the purpose very completely ; the process is cheap and 

 rapid, and the residuum, being merely a little solution of sulphate 

 of soda, is easily removed. When it is desired to employ chlo- 

 rine in place of nitric acid as the bleaching agent, the same pro- 

 cess may be adopted. 



Prof Gregory read a paper on the preexiste7ice of urea in nric 

 acid. By the action of peroxide of lead on uric acid, Liebig 

 and Wohler obtained from it oxahc acid, allantoine and urea, and 

 they considered the latter as existing in the uric acid, combined 

 with urile. The author having found that urea, unlike most or- 

 ganic substances, resists the oxidizing agency of permanganate of 

 potash, thought that if urea could be obtained from uric acid by 

 the action of that salt, the argument for its preexistence would 

 be much strengthened ; as, if only the elements of urea were pre- 

 sent, the oxidizing agency of the permanganate would most 

 likely prevent its formation. On trying the experiment, a large 

 quantity of urea was obtained, along with oxalic acid, and a new 

 acid probably formed by the oxidation of allantoine. The au- 

 thor further described the acetate of urea, a salt formed in his ex- 

 periments. 



Prof Gregory then exhibited a new process, communicated by 

 Prof Liebig, for preparing the very singular and beautiful com- 

 pound termed murexide by Liebig and Wohler, and pwpurate of 

 ammonia, by Prout. The process is quite certain, and very pro- 

 ductive. It consists in adding a boihng solution of 7 grains of 

 aloxan, and 4 grains of aloxantine in 240 grains of water, to 80 

 grains of a cold and strong solution of carbonate of ammonia. The 

 mixture instantly acquires a deep purple color, and on cooling, 

 deposits the golden green crystals of murexide. 



On the relation of form to chemical composition, by Dr. Schaf- 

 haeutl. The object of this paper is to explain the circumstan- 

 ces under which certain modifications of form take place in Gra- 

 phite, (as also in others generally considered to be elementary,) 

 and to prove their connexion with changes of an entirely chemi- 

 cal nature. 



