NOTES ON IODIDE OE POTASSIUM, ETC. 
11 
product, cannot in any way interfere with the after process. The spirit of 
nitre that has been produced from nitrite of soda thus prepared has yielded 
us, by the chloride of calcium test, 5 per cent, of separated nitrous ether, or 13 
per cent, as a whole; and in consequence of this steady yield, we have been 
obliged to reduce the proportion of nitrite used in our manufacture to meet this 
excess of strength ; the British Pharmacopoeia ruling that the spirit is to yield 
11- per cent, of nitrous ether when submitted to the test, or a total content of 
9*5 per cent. 
Assuming the specific gravity of the nitrous ether separated by the chloride of 
calcium to be *899, as stated by the Edinburgh College, or *900 as stated in the 
Dublin Pharmacopoeia’of 1826, the proportion of nitrite of soda directed by the 
British Pharmacopoeia should yield, if pure, a spirit of nitrous ether containing 
17*25 per cent.* The above result, 13 per cent., would imply a percentage of 
nitrite of soda in the salt used equal to 75*34,f a conclusion which has been 
further confirmed by the amount of nitrogen gas evolved by decomposing the 
salt with chloride of ammonium. On the same basis of calculation it would 
require the nitrite of soda used to contain 55*07 per cent, of real nitrite in 
order to produce the strength specified by the British Pharmacopoeia, and 46*32 
to bring the mixture of spirit and test liquor up to the point of saturation, or 
8* per cent.J 
Since the appearance of the British Pharmacopoeia, I have again procured 
samples of spirits of nitre from several of our leading manufacturers, but in no 
case have I yet found sufficient nitrous ether present to yield any indication 
by the test. In fact, it has been admitted that a salt containing 25 per cent, 
of real nitrite is the best product that has been obtained by the process of 
deflagration. 
Apothecaries' Hall, Blachfriars, June , 1865. 
NOTES ON IODIDE OE POTASSIUM, ETC. 
BY MR. WILLIAM IIUSKIS80N, JUN. 
The 4 Pharmaceutical Journal ’ for October last contains an interesting re¬ 
port by Mr. Clayton, in which he forms a comparison, based upon quantitative 
and qualitative analysis, between the relative values of English and Foreign 
Iodide of Potassium. The impurities in the commercial English iodide may 
be fairly considered as accidental. The chloride of potassium is derived from 
the American pearlashes employed in the process which, as is known, is never 
free from chloride, and the removal of traces of this salt is often attended with 
much difficulty, so much so, indeed, that even highly bicarbonated potash re¬ 
crystallized often contains traces of it. I suggested a process some time since 
for getting iodide of potassium free from chloride by decomposing sulphate of 
potash with iodide of calcium. With reference to the moisture it will be ob¬ 
served that cubic iodide of potassium nearly always contains free alkali, which 
secretes itself between the interstices or plates or in the cells that form the cubes 
* NaO, N0 3 : EO, N0 3 by Weight. 
69 : 75 : : 5 : 5*435 
*900 
byVol. 
6*04 in 35 of spirit of nitrous other —17*25 per 
cent. Nitrous Ether. 
f Thus:—17*25 : 100 : : 13 : 75*34; 
69 : : 4*095 : 3*767 x 20 = 75*34. 
x And ■) 9-5 x 100 
B. P. $ 17*25 
55*07. 
Vol. 
01* ; 100 : 13 :: 35 : 4*55 x 
*900 
wt. 
4*095. 
Then, 75 : 
