PHOSPHORUS. 
302.] 
245 
phorus in extraordinarily small amount, mixed with various substances, 
by heating with potash in a flask, and passing the phosphine into silver 
nitrate, separating the excess of silver, and recognising the phosphoric 
acid by the addition of molybdate of ammonia. 1 
The usual way, is, however, to produce phosphine by means of the 
action of free phosphorus on nascent hydrogen evolved on dissolving 
metallic zinc in dilute sulphuric acid. Phosphine is formed by the 
action of nascent hydrogen on solid phosphorus, phosphorous acid, and 
hypophosphorous acid ; but no phosphine can be formed in this way by 
the action of hydrogen on phosphoric acid. 
Since it may happen that no free phosphorus is present, but 
yet the first product (phosphorous acid) of its oxidation, the pro¬ 
duction of phosphine becomes a necessary test to make on failure 
of Mitscherlick’s test; if no result follows the proper application of 
the two processes, the probability is that phosphorus has not been 
taken. 
Blondlot and Dusart evolve hydrogen from zinc and dilute sulphuric 
acid, and pass the gas into silver nitrate ; if the gas is pure, there is 
of course no reduction : the liquid to be tested is then added to the 
hydrogen-generating liquid, and if phosphorous or hypophosphorous acids 
be present, a black precipitate of phosphor-silver will be produced. To 
prove that this black precipitate is neither that produced by SH 2 , nor 
by antimony or arsenic, the precipitate is collected and placed in the 
apparatus to be presently described, and the spectroscopic appearances of 
the phosphine flame observed. 
3. Tests dependent on the Combustion of Phosphine (PH 3 ).—A 
hydrogen flame, containing only a minute trace of phosphorus, or of the 
lower product of its oxidation, acquires a beautiful green tint, and 
possesses a characteristic spectrum. In order to obtain the latter in its 
best form, the amount of phosphine must not be too large, or the flame 
will become whitish and livid, and the bands lose their defined character, 
rendering the spectrum continuous. Again, the orifice of the tube 
whence the gas escapes must not be too small; and the best result is 
obtained when the flame is cooled. 
M. Salet has proposed two excellent methods for the observation of 
phosphine by the spectroscope :— 
(1) He projects the phosphorus flame on a plane vertical surface, 
maintained constantly cold by means of a thin layer of running water ; 
the green colour is especially produced in the neighbourhood of the 
cool surface. 
(2) At the level of the base of the flame there is an annular 
space, through which a stream of cold air is continually blown up¬ 
wards. Thus cooled, the light is very pronounced, and the band 8, 
1 Sonnenschein, Handbuch der gerichtlichen Chemie , Berlin, 1869. 
