354 Dr. Ure on the Ultimate Analysis of [May, 



" Cochineal seems to be made up of carbon, 15 atoms ; hydro- 

 gen, 1 1 ; oxygen, 8 ; azote, 1 . Cantharides approximate to 

 carbon, 11 atoms ; hydrogen, 10 ; oxygen, 7; azote, 1." 



" My result with urea differs so considerably in the proportion 

 of azote from that of Dr. Prout and M. Berard, that I am dis- 

 posed to doubt of the accuracy of my experiments, though they 

 were made with the utmost care, and were most consistent in 

 the repetition. I could perceive no smell whatever of nitrous 

 gas in the gaseous products, which were made to traverse a 

 column of copper filings three inches long, in a state of ignition. 

 I shall renew the inquiry on urea, and employ the lowest tem- 

 perature compatible with the formation of carbonic acid." 



" The prime equivalent of benzoic acid crystals, I find by 

 saturation with water of ammonia, to be 14*5 ; and it consists 

 apparently of carbon, 13 atoms ; hydrogen, 6 ; oxygen, 4. Of 

 crystalline citric acid, the prime equivalent is 8*375 by my expe- 

 riments ; and it consists probably of carbon, 4 atoms ; hydrogen, 

 3 ; oxygen, 5 ; or, of 4 atoms carbon, 3 water, and 2 oxygen. 

 Two of these atoms of water are separated, when citric acid is 

 combined with oxide of lead in what is called the dry citrate. 

 Hence, the acid atom is in this case 6*125. The prime equiva- 

 lent of crystalline tartaric acid is 9*25 by my results ; and it 

 seems made up of carbon, 4 atoms ; hydrogen, 2 ; oxygen, 6 ; 

 or of carbon, 4 atoms ; oxygen, 4 ; water, 2. From my experi- 

 ments I have been led to conclude, that into dry tartrate of lead 

 these two atoms of water do enter as a constituent ; and hence, 

 that the crystals of tartaric acid are as dry as is compatible with 

 its constitution. Oxalic acid crystals have 7*875 for their prime 

 equivalent, and are composed of carbon, 2 atoms ; hydrogen, 3 ; 

 oxygen, 6 ; or of 2 atoms carbon, 3 oxygen, 3 water. Into the 

 dry oxalate of lead, these 3 atoms of water do not enter. Hence 

 I find the dry acid to be composed of carbon, 2 atoms ; oxygen, 3 ; 

 or, of 1 atom carbonic acid + 1 atom carbonic oxide, as was first 

 suggested, I believe, by Dobereiner. Crystallized oxalate of 

 ammonia consists of 1 atom acid, 1 atom ammonia, and 2 atoms 

 water, = 8*875. By a gentle heat, 1 atom of water may be sepa- 

 rated ; and an oxalate of ammonia, as dry as is compatible with 

 its neutrality, remains." 



" I have analyzed, by the peroxide of copper, the citrate, tar- 

 trate, and oxalate of lead ; and on comparing the results thus 

 obtained, with those derived from the analysis of the crystalline 

 acids, I have come to the above determinations. 



" Ferroprussic acid, the ferrocyanic acid of the French che- 

 mists, has proved hitherto a stumbling block to me, in reducing 

 the results of my experiments to the atomic theory. I have sub- 

 jected it to very numerous trials in many states of combination, 

 and have sought, with great pains, to accommodate the results 

 to the doctrine of prime equivalents ; but hitherto without suc- 

 cess. The following facts, however, may perhaps be deemed of 

 some consequence. 



