Kreider— Quantitative Determination of Perchlorates. 289 
iodide ; the greater inclination of the potassium iodide tube 
made possible by this change appearing to offer advantages for 
the more gradual and regular introduction of the iodide. The 
amount of meta-phosphoric acid used was in all cases 15 em’. 
In experiment (13) heat was applied by means of a bath kept 
at 230°. 
While several of these determinations gave only admissible 
errors, the irregularity of the remainder and the uncertainty 
in striking just the proper conditions for good results, proved 
the method worthless at least in that shape. 
The experiments of Table III record the results of adding 
the acid drop by drop to an intimate mixture of the powdered 
perchlorate and iodide kept hot. 
Taste fib 
KClO,taken. KI taken. KOClO, found. Error. 
grms. erms. orms. orms. 
(14) 0°1000 4° 0°1036 0°0036+ 
(15) 0°0500 Dis 0'0502 0°0002 + 
(16) 0°0500 3° 0°0515 0°0015+ 
The high results of this table doubtless point to the dissocia- 
tion of hydriodic acid or to the partial reduction of the meta- 
phosphoric acid in the temperature, which would naturally rise 
higher where so small an amount of liquid was present. But 
when the meta-phosphoric acid was there in greater amount the 
distillation of the hydriodic acid before the complete reduction 
of the perchlorate could not be prevented. 
An ordinary mixture having thus been found insufficient to 
hold the hydriodie acid to the reduction of perchlorates, a search 
for some compound in which the perchlorate could be fused 
with an excess of potassium iodide and the mixture thus 
obtained subjected to the action of meta-phosphoric acid 
resulted in the employment of zine chloride. Anhydrous zinc 
chloride was found to fuse at about 200° C. The perchlorate 
and iodide could be added to this fusion and the whole melted, 
thoroughly diffused and cooled without any evolution of iodine. 
This mass, when treated with meta-phosphoric acid in the 
apparatus previously employed, melted gradually with a copious 
evolution of iodine. Table LV shows the quantitative action. 
The amount of zine chloride used was roughly taken about 
equal to that of the iodide. 
TABLE LV. 
KCIO, taken. KI taken. KCIO, found. Error. 
erms. orms. germs, orms. 
(17) 0°0500 5° 0°0552 0°0052 + 
(1 8) 0°0000 5° 0'0044 0°0044+ 
(19) 0°0000 4° 0°0057 0°0057 + 
