PRESENCE OF ARSENIC. 601 
indubitable, since it is a well known fact that 
phosphoric acid gives with ammoniacal nitrate of 
silver, a yellow precipitate not easily distinguish- 
able when in small quantity from that produced by 
arsenious acid; and, I find that by putting into 
Mr. Marsh’s apparatus a little of a solution of 
antimony, and a little phosphuret of lime (or other 
substance capable of yielding phosphuretted 
hydrogen) along with the usual pure sulphuric 
acid and pure zinc, and without arsenic in any 
form, gas is produced, from the flame of which a 
metallic film, or crust, may be obtained; and 
which gas, by being allowed to burn under a drop 
of water, as recommended by Mr. Marsh, gives 
the water the property of depositing a yellow 
precipitate when the ammoniacal nitrate of silver 
is added; and, in addition to this, the gas possesses 
a smell resembling, in a high degree, that of arse- 
nuretted hydrogen. 
Reflecting upon the characteristic distinctions 
which exist between arsenic and antimony, and 
participating in the anxiety to remove any embar- 
rassments prevailing against the perfection of a 
method of operating which presents such con- 
veniences as Mr, Marsh’s original discovery does, 
I have been induced to conceive that the effect 
4G 
