F. H. Storer—Scheenbein’s Test for Nitrates. 187 
process is finished. 
In experiments with lead it was found that a solution con- 
taining 00001 grm. N,O, in 50 cc. gave a decided reaction 
With iodo-starch in less than half an hour, and that a solution 
containing 000005 grm. N,O, gave a distinct reaction in half 
an hour, though it was not quite as strong as the reaction ob- 
e. 
tained with cadmium under similar circumstances. rom 
2 . ‘. S “ 
within fifteen minutes; and that a solution containing 000001 
end of two hours. With silver, an acidulated solution contain- 
Ing 0-025 grm. N,O, in 50 cc. water gave a very slight reac- 
tion with iodo-starch in the course of two hours, while a weaker 
neutral solution, containing 0°01 grm. N,O, in 100 ¢.c. water, 
that was boiled upon silver gave no reaction. : 
t is to be observed that in the foregoing set of experiments 
the solutions were acidulated in every instance before the boil- 
ing, and that an inverted condenser was always attached to the 
x in order to prevent the escape of any nitrous acid. 
Solutions containing 0-005 grm. N,O, in 50 c.c. acidulated 
Water, left in contact for eight hours or more in the cold with 
metallic aluminum, iron or zinc, and then tested with iodo- 
Starch gave no reaction in the cases of iron and zinc, and only 
4 slight coloration in the case of aluminum. , 
© reaction for peroxide of hydrogen was obtained in acid- 
