95 
ORIGINAL AND EXTRACTED ARTICLES. 
OX THE ESTIMATION OF NITRITE OF SODA. 
BY MR. JOHN T. MILLER. 
When a dilute solution of a nitrite is dropped into a solution of permanganate 
of potash to which some sulphuric acid has been added, the colour of the mix¬ 
ture fades and finally vanishes. This effect is owing to the reduction of the 
permanganic acid by the N0 3 , which by combining with two equivalents of 
oxygen is converted into N0 5 . Taking nitrite of soda, the decomposition may 
be thus represented:— 
5Na,N0 3 + 2(K0,Mn o 0 7 ) + llS0 3 = 
5Na0,S0 3 + 2K0,S0 3 + 4Mn0,S0 3 + 5NO s . 
This reaction forms the basis of a ready volumetric method of determining the 
amount of real nitrite in crude nitrite of soda. The presence of nitrate and 
carbonate of soda, or caustic soda, is immaterial. 
For example, it was required to know the percentage of nitrite of soda in a 
specimen of the crude salt, which had been made at a low temperature by the 
process of the British Pharmacopoeia. A solution in water, containing 50 
grains of the sample in 1000-grain measures, was prepared. Each decern (10- 
grain measure) contained, therefore, 0-5 grain. The strength of the solution 
of permanganate of potash was such, that to convert 4 equivalents or 112 grains 
of iron from the state of protosalt to that of persalt, 627 decerns of it were re¬ 
quired. This quantity, then, would be decolorized by 1 equivalent or 69 grains 
of nitrite of soda. 
Ten decerns of the permanganate solution were accurately measured with a 
pipette, transferred to a beaker, and mixed with 2 ounces of water and 3 fluid 
drachms of dilute sulphuric acid. 
The beaker being held over white paper, and its contents kept in brisk rotation, 
the solution of the sample was slowly dropped in—very slowly towards the end 
of the process—until, on adding another drop, the liquor became colourless. 
An inspection of the burette showed that 16-8 decerns had been used. Then 
0-5 x 16-8=8-4 grains of the sample. And as 8*4 grains decolorize 10 decerns, 
100 grains will bleach 119 decerns. Then— 
627 : 69 : : 119 : x ; x=13. 
This specimen contained, therefore, 13 per cent, of nitrite of soda. It also con¬ 
tained 13 per cent, of carbonate of soda. 
Having repeatedly obtained results similar to these, previous to the appear¬ 
ance, in the July number of the Journal, of Mr. Warington’s interesting com¬ 
munication u On Spirit of Nitrous Ether, and Nitrite of Soda,’ I was rather 
surprised on seeing the very different conclusions at which that gentleman had 
arrived. I tried the starch process carefully, but instead of 75, could find only 
11 per cent, of nitrite of soda in the product; while the carbonate of soda pre¬ 
sent amounted to 13"9 per cent. But is the u basis of calculation adopted by 
Mr. Warington quite secure? If we infer the quantity of NaO,N0 3 inthe 
salt employed from the amount of nitrous ether found in the distilled spirit, do 
we run no risk of estimating nitrate of soda as NaO,N 0 3 ? 
In order to try this point a few distillations of spirit of nitre were made, the 
salt used being in each case dissolved in twice its weight of water, as suggested 
by Mr. Warington. 
1. The nitrite of soda for this experiment was formed by keeping the nitrate 
fused for some time at a bright red-heat. When a few drops of sulphuric acid 
were added to a strong solution of it, ruddy fumes of peroxide of nitrogen ap¬ 
peared in abundance. The oxidation test indicated the presence of 42 per cent 
