us 



SEP. OP COPPER PROM SILVER, 



Ufe and applica- This Is tlie whole conftruaion ofmy pyrometer. To malce 

 ufe of it nothing more is necelTary than to introduce the p!a- 

 tina veffel A into the furnace the temperature of which is to 

 be learned. The moment the included air is a6led upon by 

 the heat it expands, and expels the water up into the gradu- 

 ated tube F F. This rife will take place accordingly as heat 

 increaies. If care be taken that the air be cooled in the vefTel 

 C as much as poffible (which will be the cafe from the large 

 furface of water to which it is expofed), it is obvious that a 

 volume of water equal to the volume of air in the vefTels of 

 platina, can never pafs up into the tube. The refrigeration 

 may be facilitated by the application of^vaporizable fluids, 

 fuch as ether, alcohol, &c. 



If the degree of temperature be obtained which the air had 

 before it was fubjecled to the experiment, and a proper al- 

 lowance be made for the pretfure of the water in F F, the 

 true cxpanfion of the air may thus be found, and compared 

 with the refpeclive temperatures. 



XXVI. 



Nciv, ecify, and economical Method of Jhparcitiji^ Copper from 

 Silver, By Mr. Goettling*. 



Sulphuric acid JL HERE are four methods of feparating copper from filver, 

 nkr1c"on'al«unt ^" ^^ "^^'^^^ f^i\mxQ the alloy to be diffolved in nitric acid. As 

 of cheapnlhTs, this acid is very dear, Mr. Geotlling thought of ufing the ful- 

 phuric in its flead, which is comparatively very cheap. His- 

 and w!th peifed fuccefs perfectly equalled his expedaticn, and the following is 

 ^""^^^- his method: 



Defciiption of Having afcertained by the touchflone, or in any other way, 

 the precefs. |j,g proportion of filver contained in the alloy, take one part 

 of fulpiiuric acid for every part of filver, and for every part of 

 copper three parts and three-fifths of a part of the fame acid. 

 Dilute the acid with half its weight of water, and pour it into 

 a matrafs on the alloy reduced to very fmall pieces. In order 



* Tranflated from Van Mons's Journal de Chtmiey Vol. VL 

 p. 77. Originally publifhed in the Tafcben-Bu^h fntr Schfideku- 

 enjtlerj and abridged by Van Mons, 



to m 



