ON THE MANUFACTURE OF OXALIC ACID. 
245 
of lead. About 240 lbs. of peroxide of lead are required for each 
168 lbs. of uric acid employed. The supernatant liquor is next 
drawn off, and the oxalate of lead washed with clear water ; this 
is then boiled with dilute muriatic acid (equal parts of acid and 
water,) by means of which oxalic acid is obtained in solution, 
which is evaporated and crystallized, whilst muriate of lead re- 
mains as the precipitate. 
The allantoin is also decomposed into oxalic acid and ammonia 
by boiling it with caustic alkali. The former unites with the al- 
kali used, while the ammonia passes over, and may be collected as 
liquid ammonia ; the oxalic acid thus generated may be obtained as 
oxalate of potash if potash be the alkali employed, or as oxalic 
acid if baryta be used, by decomposing the latter oxalate by means 
of sulphuric acid. In this case the oxalate of baryta may be 
treated in the way previously described for oxalate of lead. 
As regards these various methods of obtaining oxalic acid, their 
employment will of course always be a question of £ s. d., the 
economy of many operations of manufacturing chemistry being 
often dependent upon their adaptation to the requirements or pur- 
poses of particular manufacturers, in connection with other 
branches of manufacture carried on by them. 
The low price at which treacle and sugar are now obtainable is 
much in favor of their use in this manufacture. The chief point 
however to which attention must be directed, in order to lessen the 
cost of production of this article, is in economizing the nitric acid 
used. 
In speaking of the action of nitric acid upon sugar, it was ob- 
served that carbonic acid is produced, and that it passes off" with 
the deutoxide of nitrogen also set at liberty. The presence of car- 
bonic acid in this case proves a great obstacle in the reconversion 
of nitric oxide into nitric acid, preventing the union of the oxygen 
of the air with the nitric oxide. Various processes have been from 
time to time suggested to effect this economy in the manufacture of 
oxalic acid ; amongst these the following may more particularly be 
noticed : — 
In 1846, Mr. Jullion patented a method of converting the oxides 
of nitrogen, given off in the manufacture of oxalic acid, into ni- 
trous and nitric acids. For this purpose he uses a " generating 
