Scientific InteUigBnct. I7§ 



©f the ingot, and add to the melting mass, some silver or copper as 

 ihe case maj?- require. 



If lead or other base metal than copper, be present, it must first be 

 separated, either by saltpetre or by cupellation. 



Refiners, in general, employ 3 parts of sulphuric acid (sp. gr. 1844) 

 for 1 part of alloy, of the foregoing composition, — -varying the quan- 

 tity of acid, however, with tliat of die relative proportion of gold 

 er copper* The acid should be free from nitric or hydrochloric 

 acid. 



The only precaution requisite with respect to the copper, is, that it 

 he free from lead or tin, as these metals form, with sulphuric acid, 

 insoluble compounds which would remain mingled with the silver. — 

 In general it requires 28 parts of copper to precipitate 100 of silver, 

 and this furnishes from 100 to 104 parts of crystallized sulphate of 

 copper. 



The Platina hollers employed at Paris, were constructed by M. 

 Breant, They hold about 1 1 gallons, weight 1 8lbs. and cost 8500 

 francs. They are surrounded by an iron defence which serves to 

 transport them, and prevent injuries. Fine gold, at the moment ia 

 which it is separated from the alloy, by sulphuric acid, is in very fine 

 powder, which coming in contact with the platina, under the influence 

 <of boiling acid, is easily soldered to the platina, and requires to be 

 detached from time to time, by the action of a little weak aqua regia 

 which dissolves the gold without attacking the platina. — Bib. Univ.. 

 Avril, 1829. 



21. Pectic acid convertible into oxalic hy an alkali. — In a memoir 

 on pectic acid and on carrots, by M. Vauqnelin, read to the Academy 

 of Sciences, April 27, 1829, the following method is recommended 

 for preparing pectic acid. 



Take carrots, of the yellow variety, and after having rasped thena 

 and pressed the pulp, and washed it with common rain-water until it 

 comes off quite limpid, convert it into a pap by boiling it gently in a 

 solution of bi-carbonate of potash (5 parts of bi-carbonate to 100 of 

 the pressed pulp.) By pressing this pap, (bouillie,) a liquor is ob- 

 tained highly charged with pectate of potash, from which the pectic 

 acid may be easily obtained, by treating it with an excess of hydro- 

 chlorate of lime, washing, and treating the insoluble pectate of lime 

 with water sharpened with hydrochloric acid, and then washing it 

 with pure water- The pectic acid thus obtained is much whiter tliaa 

 when caustic potash is employed^ 



