of Edinburgh, Session 1885 - 86 . 
643 
men contains of high importance. For while to most patients a dose 
of five or six grains of pure, or nearly pure, nitrite of sodium is as 
large a quantity as they can conveniently bear, we read* * * § of twenty 
and thirty grains of so-called nitrite of sodium having been adminis- 
tered without dangerous or very unpleasant results. In such cases 
we cannot but conclude the drug was impure, and MacEwan f has 
shown that samples of nitrite of sodium were met with in commerce 
containing but a decimal percentage of the salt. Many papers J 
have recently appeared on the estimation of nitrite of ethyl in the 
spirit of nitrous ether, but in this contribution I desire only to con- 
sider those methods suitable for the estimation of nitrous acid in its 
inorganic compounds. While many methods are employed for this 
purpose, that chiefly followed in pharmaceutical chemistry is one or 
other of the modifications of the permanganate process, a process 
first applied to the volumetric estimation of inorganic nitrites by 
Feldhaus.§ He presumably obtained the idea from Forchhammer 
of Copenhagen, who in 1850 described a process for the estimation 
of organic matter in potable waters by permanganate of potassium. 
The process, as applied to nitrites, depends upon the power of per- 
manganate of potassium, especially in the presence of free acid (pre- 
ferably sulphuric), to oxidise nitrous to nitric acid, as may thus be 
expressed in the case of nitrite of sodium : — 
4H 2 S0 4 + 2KMn0 4 + 5FTa.N0 2 = 2MnS0 4 + 2KHS0 4 
+ 5NaN0 3 + 3H 2 0. 
Taking the same example, it is obvious that to estimate the per- 
centage of actual nitrite in commercial nitrite of sodium, all we 
require is to ascertain the amount of permanganate (representing a 
certain quantity of oxygen) which a given quantity of the commer- 
cial nitrite can decolorise, and compare it with the quantity which 
would be decolorised by an absolutely pure nitrite. This latter 
quantity is readily enough ascertained from the atomic weights of 
the elements. The simplest method of estimating the amount of 
* See especially the Practitioner, vol. xxx. p. 109. 
t Pharmaceutical Journal , 3rd series, vol. xiii. p. 121. 
+ Consult papers by Dott, MacEwan, Eykman, and Allen, in Pharmaceutical 
Journal , 1882-85. 
§ Archiv der Pharmacie, April 1860. 
