ON NITRITE OF SODA. 
cipal compound (the nitrite of soda) used in its manufacture, there appears to 
be some difficulty. We are told to take nitrate of soda, and this is defined 
to be pure, entirely soluble in water and giving no precipitate with either nitrate 
of silver or chloride of barium, showing absence of mechanical impurities, sul¬ 
phates, and chlorides. This pure nitrate of soda, quite dry and in fine powder, 
is to be thoroughly mixed with freshly burned charcoal, also in fine powder ; 
the mixed powders are then to be thrown in successive portions into a clay 
crucible heated to dull redness, and when the salt has become quite white the 
heat is to be raised, so as to liquefy it, and it is then to be poured out on a clean 
flagstone, and when cold broken to pieces and preserved for use in a stoppered 
bottle. 
Thus far the Pharmacopceial directions, and now for my own experience of 
this process. I operated on one pound of commercial nitrate of soda, and an 
ounce and a quarter of powdered charcoal, and obtained about twelve ounces of 
a dirty reddish-brown and very impure salt. The next point was to ascertain 
the quantity of nitrite it contained, which I did by trying to dissolve a portion 
in rectified spirit, as the Pharmacopoeia tells us it is soluble in that menstruum. 
On treating a weighed quantity with successive portions of rectified spirit, 
I found forty-four per cent, were soluble; this I considered favourable, as I was 
operating on commercial nitrate, which I knew could not be pure. 
I then tried what results could be obtained with pure nitrate of soda, so by 
dissolving the commercial nitrate, filtering and crystallizing the solution, I ob¬ 
tained a beautifully clean and pure salt. I again submitted the same proportions 
to deflagration, but, contrary to my expectations, the product was coloured, 
though not so deeply as in the first instance, and the crucible appeared to have 
been acted on by the fusion of the salt; the result, however, was an improve¬ 
ment on the former one, for it contained sixty-eight per cent, of salt soluble in 
rectified spirit. 
I next tried a thin white kind of crucible, and subsequently one of blacklead, 
but still the product was coloured; the yield of soluble salt in rectified spirit 
was between sixty and seventy per cent. 
Of two samples I obtained from manufacturing chemists, one contained sixty 
and the other sixty-six per cent. 
I found the salt which was dissolved out by rectified spirit to answer the 
Pharmacopoeial test for nitrite of soda, namely :— 
P'he evolution of nitrous fumes with tartaric acid. 
A crystalline precipitate soluble on boiling the liquid with nitrate of silver. 
And, 
An emerald-green coloration with solution of sulphate of copper. 
It also required one ounce of rectified spirit to dissolve ten grains of the salt. 
It now remained to ascertain if nitrate of soda was soluble in rectified spirit, 
and, if so, to what extent. I found four grains to be dissolved by a fluid ounce 
of cold rectified spirit. 
So that from this it appears that the solubility of this salt in rectified spirit is 
no test of its freedom from nitrate. The form of the crystals will not help us, 
for Gmelin states the nitrate and nitrite have both the same crystalline form. 
AVhat is required seems to be a good quantitative test, and also a good process of 
the manufacture of this salt. The intention of the framers of the Pharmacopoeia 
has been excellent, and this is a step in the right direction. 
I regret I am unable to bring any more definite results before you, but hope 
to do so at a future day. Having thus started the subject, I hope some others 
who may have been labouring in the same field will favour us with their 
experience. 
I have a specimen of the spirit of nitre on the table, prepared from the im¬ 
pure nitrite of soda ; its specific gravity is *840, rather lighter than British Phar- 
