80 
ill the determination of copper and iron in water, for 
which the method is specially applicable, a measured quan- 
tity is evaporated with a few drops of nitric acid to dryness, 
ignited to get rid of any organic matter that might colour 
the liquid, and dissol\^ed in a little boiling water and a di’op 
or two of nitric acid, if it is not ail soluble it does not 
matter ; ammonia is next added to precipitate the iron, the 
latter filtered off, washed, redissolved in nitric acid, and 
again precipitated by ammonia, filtered off and washed. 
The filtrate is added to the one previously obtained, and the 
iron estimated in the precipitate and the copper in the 
united filtrate. 
The distilled water used in the Owens College Laboratory, 
and which is condensed by the apparatus made by Hirzel 
of Leipzig, gave, on analysis by the above method, the 
following results, two litres of the water being used for the 
purpose : — ■ 
015 paits Cr. 1 1 000,000 parts of water. 
0-03 parts Fe. j ^ 
The copper and iron in this case were evidently derived 
from the fittings of the condensing apparatus, v/hich con- 
sisted in great part of these metals. 
