1907-8.] Nitric Anhydride as a Nitrating Agent. 
705 
XLIII.— Nitric Anhydride as a Nitrating Agent. 
By G. E. Gibson, B.Sc. 
(MS. received July 24, 1908. Read July 13, 1908.) 
In the ordinary methods for the preparation of tartaric acid dinitrate, a 
mixture of fuming nitric acid with concentrated sulphuric acid is used as 
a nitrating agent. 
The product is treated with iced water to remove the sulphuric and 
nitric acids. 
As the dinitrate is decomposed by water, even at 0° C., it is impossible 
to avoid some loss in this process. 
By using nitric anhydride as a nitrating agent this difficulty is avoided. 
Nitric acid, which is the only other product of the reaction, can be removed 
by evaporation in vacuo. 
The ordinary methods for the preparation of nitric anhydride are some- 
what troublesome. By the method described below, several hundred grams 
of nitric anhydride can be prepared in a day. 
In the figure, A is a tubulated retort of 3 litres capacity, the neck of 
which has been bent to a right angle. 
B is a glass dropping funnel of about 700 c.cs. capacity, the delivery 
tube of which is ground into the tubule of the retort. C is a platinum or 
glass receiver of about 1 litre capacity. It is surrounded by a freezing 
mixture of ice and salt. 150 grams of phosphoric anhydride are introduced 
into the retort, and the dropping funnel containing 500 c.c. of nitric acid 
(sp. gr. 1-52) is placed in position. From 200-300 c.c. of nitric acid are 
slowly dropped into the retort, and the mixture is left to stand, with 
occasional stirring, till nearly all the phosphoric anhydride is hydrated. 
A stout glass rod, bent 3 inches from the lower end to an angle of 30°, 
is used to stir the mixture. To prevent loss of nitric anhydride, the space 
between the rod and the inside of the tubule of the retort is closed with an 
asbestos wad, which is made air-tight by means of a little of the syrupy 
mixture in the retort. The wad is easily made by wrapping asbestos paper 
round the glass rod. 
450 grams of phosphoric anhydride are now added and the remainder 
of the nitric acid is dropped in. 
The process is completed by cautiously heating the retort, with occasional 
stirring. 
VOL. XXVIII. 
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