430 Scientific Intelligence. 
action of acids. The cause of this color seemed to me at first obscure, 
but I found that by adding a very minute quantity of freshly —— 
sulphuret of iron to solution of protosulphuret of potassium, the sam 
color was produced, and a sensible trace of iron may always be found in 
Er ra ih 
A greenish color is frequently observed when sulphuret of iron is pre- 
cipitated in the presence of an alkaline sulphuret, but as it disappears o 
standing, it has ‘taoeg commonly attributed to the presence of particles of 
- sulphuret of iron held in — an opinion which must be erroneous, 
since I have obtained a solution of iron in sulphuret of Spamaiin of an 
intensely green color perfectly one and transparent, and permanent for 
many days in a sealed tube. 
Why this green compound should be formed under some ——— 
ces, and not under others, in a mortar, and not in a cannon, is not i 
_ ceptible of explanation. 
t has been shown that when powder is exploded under slight pressure 
the ralbeline metal remains in large part as a sulphate, but under higher 
pressure and corresponding temperature, it is reduced to the condition of 
a sulphuret. Now, by analogy, it would seem, that ike pe ordinary 
charges of a cannon or musket the iron is not reduced to the state of sul- 
phuret, but if, as is often the case in a mortar, the projectile is bap times 
the weight of the powder, or upwards, the gases are brought to a state of 
great some before the shot moves, and in that state of things “the car- 
bon is completely converted into carbonic acid, _ the iron, as well as 
the potassium, brought to the condition of sulphur 
Smithsonian Laboratory, Washington, D. C., 0. 
15. On the Amounts of Lead contained in some Silver Coins ; by Extor 
and Srorer.—The determination of the amount of lead in American sil- 
ver coin was suggested to the authors by finding half of one per cent of 
lead in a sample of zinc such as is used at the United States mint for re- 
ducing chlorid of silver. (See their Memoir on the Impurities of Com- 
mercial Zine in Memoirs Amer. Acad. [N. 8.], viii, 61; also this Journal, 
[2], xxxi, 142). For the sake of comparison other coins were subse- 
quently examined. 
Per cent of Lead 
Kind of coin. in the coin. 
1 American halt: dollar of 1824, - - = 0-310 
20 five-cent pieces of 1853, - - - 0209 
oe = - n-ce a 4 of 1864,. << - - 0°228 
wenty-five cent pieces ati 0-231 
. Fine Sie from the U.S. Assay Office in x. York, 1860, 0-161 
1 nish dollar of 1793, agai IV, 0°056 
exican “.,..* 9, - - - 0:043 
: English Shillings of 1816, - 0°485 
1 French five-frane piece of 1852, Napoleon I, - 0°428 
On the supposition that the zine used in the reduction of the silver is 
the source of the lead in the American coin, the authors calculate the 
amount of lead which would thus find its way into the coin. Their me- 
moir, already cited, gives the per cents of lead found in two specimens 
Vieille Montage zinc; if zine of the best quality (containing 0-292 Per 
a 
