ON THE MANUFACTURE OF OXALIC ACID. 
U7 
liquor, and the temperature raised as quickly as possible to 180° 
or 200° F. Streams of nitric acid and syrup are then caused to 
flow into the generator by means of suitable stop-cocks and funnel- 
pipes, in such a quantity that the delivery of the whole shall oc- 
cupy about eighteen hours, at the expiration of which time the pro- 
cess will be completed. 
The gases arising from the decomposition of the materials so 
supplied pass off through an eduction-pipe in the top of the gene- 
rator into a receiver, into which a stream of chlorine is introduced 
(from a chlorine-generator) sufficient to convert the whole of the 
oxides of nitrogen into nitric acid. A portion of the water in the 
receiver is decomposed, its oxygen combining with the oxide of 
nitrogen to form nitric acid, whilst its hydrogen combines with 
the chlorine to form hydrochloric acid. These mixed vapors pass 
over into suitable condensing vessels placed to receive them. The 
whole of the nitric acid and syrup having been run in, and the 
liberation of the gases or oxides of nitrogen having ceased, the 
oxalic acid liquor is drrawn off from the generator and crystal- 
lized. 
Messrs. McDougall and Rawson have also patented a method of 
recovering the vapors which pass off in the manufacture of oxalic 
acid. To effect this, they direct the employment of a series of ves- 
sels containing water, into the first of which the nitrous gas or 
fumes are passed through a tube dipping below the surface of the 
vessel ; air is also admitted, which mixes with the gas bubbling up 
through the water. Attached to the last vessel of the series is a 
pneumatic apparatus, by means of which the mixture of nitrous 
gas and air is drawn through this series of vessels, each contain- 
ing a tube dipping into the liquid, and another tube or pipe at- 
tached to its top to connect it with the next vessel. The nitrous 
gas thus passing alternately into air and water, becomes converted 
into nitric acid. In this process the following reaction is said to 
take place : — 
On 3NO* being passed into water of the temperature of 100°F., 
or upwards, 2N0 5 +N0 2 result, the 2N0 5 , i. e. 2 atoms of nitric 
acid, remain in solution, whilst the NO 2 , which is an inconden- 
sable gas, bubbles through the liquid and unites with the air in the 
vessel above the liquid ; it immediately takes 2 atoms of oxygen 
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