=374. Nitric Acid.=—Any nitric acid or nitrate which an agricultural
product may contain may be leached out by treating the fine-ground
material with cold water. From vegetable matters this extract is
evaporated to a small bulk, filtered, if necessary, and tested for
nitric acid by the usual treatment with ferrous sulfate and sulfuric
acid. In the case of vegetable substances there will not usually
be enough of organic matter to interfere with the delicacy of the
reaction, but in animal extracts this may occur. Colored extracts
should be decolorized with animal char (bone-black) before they are
subjected to examination. It is not well to attempt to remove the
organic matters, but, since they are more insoluble in water than the
nitrates, the solution containing both may be evaporated to dryness
and treated with a quantity of cold water insufficient for complete
solution. The nitrates will be found in the solution obtained in a
larger proportionate quantity than before.
=375. Amid Nitrogen.=—One or more atoms of the hydrogen in ammonia may
be replaced by acid or basic bodies (alcohol radicles). In the former
cases amids, in the latter amins result. In the ratio of displacement
there are formed primary, secondary, and tertiary bodies determined by
the number of hydrogen atoms replaced. The primary amids are the only
ones of these bodies that are of interest in this connection.
The amids are easily decomposed, even on heating with water and the
more readily with acids and alkalies, the amido radicle being converted
into ammonia. A type of these reactions is given below.