” 
* 
e. 
188 Wollaston’s Camera Lucida. 
and certain manipulation, dependent upon a standard of light 
of constant intensity, and easily reproduced in all situations. 
—Idem. 
20. loduret of | hex cwyoteee substance being now em- 
ployed in medicine, the following method of preparing it,” 
as stated by es Pharmacein, of Paris, may be of some 
importance. “1 take four parts of iodine, two of iron filings 
free from rust, and about twenty of water ; I put the en 
substances in a capsule of glass or porcclain,commencing w 
the iodine and water. I keep stirring until the liquor, whic 
soon acquires a deep brown colour, becomes colourless; 
then I place the capsule over the fire, and when the liquid 
boils, I pour in by degrees, stirring it each time, a solution 
of pure subcarbonate of potash, until there is no longer a 
precipitate ; or rather I adda slight excess of carbonate of 
Such which J saturate with hydriodic acid, after filtration. 
decant upon a filter, and I wash the residuum as long as the 
water which passes through it occasions a precipitate, with 
the deuto-chloruret of mercury: 1 then reunite all the 
liquors and evaporate to a pellicle. 
The same procedure may be applied to the preparation 
of the Todurets of sodium, magnesium, calcium, barium, 
and strontium, —that is to say, in boiling the ioduret of iron 
with magnesia. soi barytes, strontian, or the subcarbon- 
aes of these bas 
We may liketies prepare the ioduret of mercury, by de- 
composing the proto-nitrate of mercury, and the deuto- 
chloruret by the ioduret of iron, which, as has just been 
shown, may be extemporaneously prepared. —An, de Chi- 
mie, Feb. 1823. 
21. The Camera Lucida of Dr. Wollaston has been so 
modified by J. B. Amici, a professor of Modena, as to re- 
tained of Lerebours, optician to the Bureau of Longitad>, 
place de Pont-Neuf, 4 Paris —Jdem. 
