246 POISONS : THEIR EFFECTS AND DETECTION. [§ 303 . 
which is almost invisible in the ordinary method of examination, is 
plainly seen. 1 
An apparatus (devised by Blondlot, and improved by Fresenius) for 
the production of the phosphine flame in medico-legal research is repre¬ 
sented in the diagram given below. 
Several of the details of this apparatus may be modified at the con¬ 
venience of the operator. A is a vessel containing sulphuric acid ; B is 
partly filled with granulated zinc, and hydrogen may be developed at 
pleasure ; c contains a solution of nitrate of silver ; d is a tube at which 
the gas can be lit; e, a flask containing the fluid to be tested, and pro¬ 
vided with a tube/, at which also the gas issuing can be ignited. The 
orifice should be provided with a platinum nozzle. When the hydrogen 
has displaced the air, both tubes are lit, and the two flames, being side 
by side, can be compared. Should any phosphorus come over from the 
zinc (a possibility which the interposed silver nitrate ought to guard 
against), it is detected ; the last flask is now gently warmed, and if 
the flame is green, or, indeed, in any case, it should be examined by 
the spectroscope. 2 
§ 303. The spectrum, when fully developed, shows one band in the 
orange and yellow between C and D, but very close to D, and several 
bands in the green. But the bands 8, y, a, and are the most 
characteristic. The band 8 has its centre about the wave-length 599-4 ; 
it is easily distinguished when the slit of the spectroscope is a little 
1 Consult Spectres Lumineux, par M. Lecoq de Boisbaudran, Paris, 1874. See 
also Christoflo and Beilstrom’s “ Abhandlung,” in Fresenius’ Zeitschr. f. anal. Chern ., 
ii. 465, and iii. 147. 
2 F. Selmi has proposed the simple dipping of a platinum loop into a liquid con¬ 
taining phosphoric acid, and then inserting it into the tip of a hydrogen flame. 
