The precipitate contains 80.09
per cent. uranium oxide and 19.91 per cent. of phosphoric oxide. What
percentage of uranium oxide was contained in the uranic acetate?
NITROGEN AND NITRATES.
Nitrogen occurs in nature in the free state, and forms about four-fifths
of the atmosphere. In combination, as nitrate, it is found in nitre
(KNO_{3}), and Chili saltpetre (NaNO_{3}), minerals which have a
commercial importance. The latter occurs in beds, and is extensively
worked for use as a manure and in the preparation of nitric acid.
Nitrogen is mainly characterised by negative properties, although many
of its compounds are very energetic bodies. It is a gas, present
everywhere, but so inactive that the assayer can always afford to ignore
its presence, and, except in testing furnace gases, &c., he is never
called on to determine its quantity.
The nitrates are an important class of salts, and may be looked on as
compounds of the bases with nitric pentoxide (N_{2}O_{5}). They are,
with the exception of a few basic compounds, soluble in water, and are
remarkable for the ease with which they give up their oxygen. The
alkaline nitrates fuse readily, and lose oxygen with effervescence
forming nitrites; while at a higher temperature they yield more oxygen
and lose their nitrogen, either as a lower oxide or as nitrogen.
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