420 Scientific Intelligence, 
regret it. This formula is less empirical than it seems, for it is the te 
sult of a long series of researches and trials, eye which “ on 
be useless to dilat: Such as it is, it is good, and has given 
several years very peuitatt results; and, | may add, that cries ‘thet 
collodions, time has upon it no other influence than to improve it, 
which has determined me always to have a supply a year old on han 
Formula, 
For ; eo of collodion, == 35} fluid ounces. 
Ether 800 grammes, 284. ae 
Alc : a 250 * 88 “ Na 
soluble gun pane 8 i 123 grains. 
Todi of cadmium 9 2 139 
Upon complete, talitici twenty-five drops of pure bromine are added. 
The color becomes very intense, for there is some iodine set free, and a 
consequent formation of bromid of cadmium. om this litre I extract 
100 grammes—one tenth part of the whole Giiantihy one ii place in 
a separate flask. Into this 100 grammes are dropped twelve or thirteen 
rops of highly concentrated liquid ammonia. A very thick golden- 
ellow precipitate is formed, so thick that it will not mingle with the 
a filers se even by vigorously shaking the flask. It is not easy 
to define with chemical exactness the eonstitation of this precipitate; 
but whats is certain is, that it suffices to add to it a few drops of crys 
tallizable acetic acid to dissolve it and render eh’ collodion pe rfectly 
limpid. This last operation with acetic acid is somewhat uncertain, & 
the quantity varies according to the quality of the alcohol and ammo 
used. I now pour back into the first Hask the 100 grammes upon 
which I have just speiton: and let the whole stand for fifteen days 
before using it. During this time the collodion, however red on : 
e, changes gradually until it attains at last a pale straw-color, W 
tint it ought to keep. If the collodion is found to be insuficlony 
t 
iodized (althongh the 7 adie wou above given sin _ oo, of 3 
ne Ag er stals of amtabs of silver; I have never had any reason ! 
see of this, on the contrary I think it is to the reaction wh" 
duces them that we iia ie te the good qualities of this 
III. METALLURGY. 
W. T. Roeper, (communi at ; 
ia ras pen big oie the he mais! 
te rears 
