120 
J. A. Baker 
11 . Potassium permanganate. The pure salt was dissolved 
in water, about 4 grams being taken for each liter of water. This 
was standardized according to the two following methods: 
a. With metallic iron. Thin annealed wire, containing 99.6 
per cent of pure iron was dissolved in dilute sulphuric acid, in an 
Erlenmeyer flask fitted with a Bunsen valve. Heat was usually 
applied to hasten solution. When solution was complete the flask 
and contents were cooled without removing the stopper, by holding 
under a stream of water. The stopper was then removed, the 
liquid was diluted, if necessary, with recently boiled, distilled 
water, and the iron was titrated with the permanganate solution 
to a faint pink color. The calculation for the iron value of the 
permanganate was made as follows : 
Weight of iron wire taken 
Weight of iron in {a) = (a) X .996 
Volume of permanganate used 
I cc. of permanganate = (h) -f- (r) 
= .xxxx (a) 
= .xxxx (b) 
= .xxxx (c) 
= .xxxxx g. Fe 
b. With ferrous ammonium sulphate. Weighed portions of 
the salt were dissolved in acidulated water in a flask into which 
had been previously put a little sodium carbonate. The water 
was acidulated with sulphuric acid. As soon as solution was com- 
plete the iron was titrated with the permanganate solution, and 
the value of the latter calculated as follows : 
Weight of (NH,)^ Fe {pop, m,0 = .xxxx (a) 
Weight of iron present == (a) X .14251 = .xxxx (b) 
Volume of permanganate used = .xxxx (r) 
I cc. of permanganate = (b) {c) = .xxxxx g. Fe 
Since the purpose of the permanganate solution in the work 
undertaken was to determine antimony, the iron value as found 
above was calculated to the antimony value as follows: 
The equations for the action of permanganate upon iron com- 
pounds and upon antimony compounds are these: 
2KMnO, + loFeSO, 4- = 5Fe2(SOj3 + K^SO^ + 2MnS04 + m ,0 
2KMnO, f sSbClg + 16HCI = 2MnCl3 + s’ShCl- + 2KCI + SH^O 
It is apparent, then, that 10 atoms of iron are equivalent to 5 atoms 
of antimony in reducing KMnO^. Hence the following propor- 
tion will give the antimony value of the permanganate [solution. 
