292 Kreider— Quantitative Determination of Perchlorates. 
In (81) manganous chloride was mixed with the zine chloride 
in the proportion of 2:1 in the hope of strengthening the 
reducing action. The black color of the fusion revealed the 
formation of manganese dioxide, the equivalent of which in 
iodine was obtained by dissolving the cooled mass in water, 
adding dilute sulfuric acid and a known amount of ammonium 
oxalate, titrating the residual oxalate with permanganate solu- 
tion and calculating the difference into iodine which was added 
to that obtained by tritrating the contents of the receivers. 
This addition of manganous chloride to the fusion of the double 
chloride of aluminum and sodium was forestalled by the neces- 
sity of subsequent solution of the fused mass, which contained 
an impurity in the form of ferric chloride, which of course in 
the presence of hydriodic acid would be reduced with evolution 
of iodine. 
It was evident from all these results, as well as those obtained 
by use of other salts not necessary here to record, that fusion 
with salts of the halogens would not suffice for the complete 
reduction of perchlorates, or at least would not quantitatively 
register the result in the halogen liberated. The well known 
reaction of the oxidation of chromic oxide by fusion with alka- 
line carbonates was also applied. A combustion tube was used 
for the fusion, sealed at one end and, after the insertion of 
chromic oxide with a mixture of sodium and potassium carbon- 
ate, restricted at the other end so as to admit a small tube by 
which carbon dioxide could be entered to expel all air. A 
blank determination gave no chromate. When 0-1 grm. potas- 
sium perchlorate was mixed with an excess of chromic oxide 
and alkaline carbonate and carefully fused from the top and 
kept in a state of fusion throughout its length in an atmosphere 
of carbon dioxide, the fusion subsequently dissolved in water 
and the chromic oxide removed by filtration, an amount of 
chromate was obtained on titration equivalent to only 0:0347 
erms. of potassium perchlorate. 
Powerful as were the various reducing agents employed for 
the decomposition of perchlorates, they were all successfully 
resisted, even at the highest permissible temperatures; and if 
anything is proved by the results of the experiments above 
recorded, it is that perchloric acid is, in. combination, one of 
the most powerful and stable acids known. Certainly nothing 
short of high temperatures is capable of overcoming the 
remarkable affinity by which the oxygen of this acid is held 
by its salts. At about 400° C the potassium salt fuses with 
evolution of oxygen, and as a last resort an attempt was made 
to have the oxygen thus obtained act on hydriodie acid by 
intervention of nitric oxide. It was the application of this 
principle that led to the final method, which both as to manipu- 
lation and results leaves nothing to be desired. 
