ARGENTINE COMPOUNDS, SPREAD ON PAPER, SENSITIVE TO LIGHT, ETC. 329 
My first attempts at producing, by this means, extensive surfaces, were failures; 
the paper generally presented a gray silver spot surrounded by a series of highly co- 
loured rings, and an external one of a velvet black ; these were of course phospho- 
rus and silver in various proportions. Even in this state, sunshine appears to have 
some effect upon the papers ; the inner most circles, the redand yellow, pass with tole- 
rable quickness into different shades of olive. 
By exposure to iodine the coloured rings are attacked, and changed in their cha- 
racters, long before any influence is apparent on the pure silver spot, generally, but 
not always, assuming their complementary colours. The sensitiveness of these bands 
is as their position ; the black exhibiting a decided action, which lessens in every 
ring, and is lost on the verge of the gray silver. If the silver is allowed to assume 
the required golden hue from the iodine, the order of sensitiveness is reversed. 
15. To prevent explosions of this spontaneously inflammable gas, I have, amongst 
other methods, used the vapour of ether. When this has been the case, at the mo- 
ment of reduction a portion of carbon appears to be separated from the ether, and, 
combining with the phosphorus, is deposited on the paper, forming a band of a 
yellow brown tint, which is sometimes found within and at others without the coloured 
circle, the place appearing to depend on temperature. I was at first inclined to con- 
sider this as a simple combination of phosphorus and carbon ; but the sensitiveness of 
the band inclines me to the opinion of its being a carbo-phosphuret of silver. I should 
state that it stands next to black in the order of sensibility : I find the same effect is 
produced by dissolving the nitrate of silver, with which the paper is washed, in spirits 
of wine. 
16. By very carefully spreading a strong solution of the nitrate of silver over a 
highly-calendered paper, and then exposing it to the perphosphuretted hydrogen slowly 
evolved from the phosphuret of lime, a very even metallic surface was formed, from 
the leaden colour of which it may be concluded some phosphorus had entered into 
combination with the silver. This paper was soon attacked by the iodine, was little 
less sensitive than the silvered copper, but it was scarcely possible to remove the 
iodine, so as to preserve the picture when complete, without portions of the surface 
breaking away, so slight was the adhesion between the paper and the metal. 
17- By allowing the paper to absorb the silver solution, and to become nearly, but 
not quite dry before exposed to the gas, and the gas, which I usually form from phos- 
phorus and solution of potassa, being liberated in large quantities, a black paper 
possessing in a very eminent degree all that is desired, is the result. 
Unfortunately, however, although I have used every precaution, I find it im- 
possible to prepare more than a dozen quarter-sheets without an explosion of the gas. 
In placing and removing the paper, atmospheric air necessarily enters the vessel, be- 
sides which, a quantity of oxygen sufficient to occasion spontaneous inflammation is 
set free from the nitrate of silver and the water absorbed by the papers. On one oc- 
casion I so placed and arranged some papers in a vessel as to do away with the pos- 
mdcccxl. 2 u 
