646 
Proceedings of the Royal Society 
4. A one per mille Solution of the Nitrite to he investigated . — 
In the case of such nitrites as nitrite of silver, where the metal has a 
high atomic weight (Ag=108), it is advisable to use 2 per mille. 
Blit as usually nitrite of sodium or potassium is the nitrite in ques- 
tion, 1 in 1000 is the most suitable strength. Now, as we are deal- 
ing with the action of reducing agents on permanganate of potassium, 
a question first started, so far as I know, by Jones,* comes under 
consideration. He states that the action of oxalic acid, of ferrous 
sulphate, and of some other substances with which he has experi- 
mented on permanganate of potassium, in strong or in dilute solu- 
tion, and with or without the presence of sulphuric acid, is accom- 
panied by the evolution of oxygen, and, as he mentions, such a 
statement has an important hearing on the use of permanganate in 
volumetric analysis. I have repeated some of Jones’s experiments, 
and while agreeing with him that in strong solution such an evolu- 
tion of oxygen does occur, I am quite unable to find any evidence 
of the evolution of this gas with the dilute solutions I have men- 
tioned. Moreover, the check experiments I shall shortly allude to 
confirm me in my opinion that no such fallacy can arise in this 
modification of the permanganate process. But if no oxygen be given 
off during the reduction of the permanganate, is none given off when 
one adds the sulphuric acid to the potassium salt (the permanganate) ? 
I have estimated the amount of oxidising power possessed by a mix- 
ture of the permanganate and sulphuric acid solutions after standing 
for periods varying from a few seconds to 30 minutes, the reducing 
agent being a solution of ammonio-ferrous sulphate, and have found 
no diminution in strength. After boiling for some time a mixed 
solution of permanganate and sulphuric acid, and then estimating 
the oxidising power, there is certainly a marked but not very great 
diminution : — to 200 c.c. of distilled water, 50 c.c. of permanganate 
solution (1 per 1000) and 10 c.c. diluted sulphuric acid (1 in 10) 
were added, and the mixed solutions at once titrated against ferrous- 
ammonium sulphate solution, of which 53*25 c.c. were used. A 
similar mixture was gently boiled in a glass flask for three hours, 
when only 50*34 c.c. of the reducing agent were required to effect 
complete decoloration. Repetitions of the experiment gave very 
similar results. Further, in connection with the possibility of oxygen 
* Journal of the Chemical Society , vol. xxxiii. (new series), pp. 95-101. 
