REPORT ON CHEMISTRY. 
tained by boiling cyanuric acid with a saturated solution of urea. 
It is soluble in alcohol, and decomposed by nitric acid into cy¬ 
anuric acid and nitrate of urea. 
Purpuric acid .—Some degree of light is thrown upon the 
nature of purpuric acid by the process for preparing it given 
by Quesneville *. He dissolves uric in nitric acid in the pro¬ 
portions given by Dr. Prout, saturates the acid with ammonia, 
and precipitates with acetate of lead. The precipitate is of a 
beautiful rose-red. Decomposed by sulphuretted hydrogen in 
excess, the colourless acid of Vauquelin is obtained ; if not em¬ 
ployed in excess, the acid is of a red colour. This would seem 
to argue that a deoxidation takes place when the colour is de¬ 
stroyed. 
Erythric acid .—Kodweiss has found that the nitric and pur¬ 
puric acids combine when the latter is dissolved in a weak so¬ 
lution of the former, and give by gentle evaporation small rhom- 
boidal crystals, which imperfectly saturated with ammonia have 
the characters of Brugnatelli’s erythric acid. This agrees with 
the previous observations of Dr. Prout. 
On the other hand, if uric be dissolved in excess of nitric 
acid, colourless crystals of a compound of purpuric and oxalic 
acids are obtained. They may also be prepared by dissolving 
purpuric in nitric acid, and adding oxalic acid. Bases decom¬ 
pose this double acid, giving an oxalate and a purpurate. Kod¬ 
weiss observes also, that in every case of the decomposition of 
uric by nitric acid, urea is formed ; which may be separated by 
alcohol from the solution previously saturated with oxide of lead 
and concentrated to the consistence of a sirup. 
Lactic acid .—Mitsclierlich (Lehrbuck, i. p. 50,) gives the fol¬ 
lowing process for preparing pure lactic acid. Lactate of lead 
prepared in the usual way is decomposed by sulphate of zinc, the 
sulphate of lead separated, and the lactate of zinc crystallized by 
evaporation : at first it is yellow, but by repeated crystallization 
is obtained of a pure white. The solution of this lactate is de¬ 
composed by caustic barytes, the oxide of zinc separated, and 
the lactate of barytes which is in solution decomposed by sul¬ 
phuric acid, and evaporated, gives a clear, colourless, sirupy 
acid, not volatile, but decomposing and leaving a residue of 
charcoal when heated to a sufficiently high temperature. 
Milk .—Braconnotf has published some observations on milk 
and cheese. 
The following preparation suggested by him might probably 
be advantageously employed at sea. Fresh curd is boiled in 
* Journ. de Chim. Medicate, iv. p. 225. 
f Annates de Chim. xliii. p. 337. 
