Scientific Intelligence. 179 
of the ingot, and add to the melting mass, some silver or copper as 
the case may 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 that of the relative proportion of gold 
or copper. ‘The acid should be free from nitric or hydrochloric 
acid. 
The only precaution requisite with respect to the copper, is, that it 
be 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 boilers employed at Paris, were constructed by M. 
Bréant.. They hold about 11 gallons, weight 18lbs. and cost 8500 
franes.. They are surrounded by an iron defence which serves to 
transport them, and prevent injuries. Fine gold, at the moment in 
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 by an alkalh.—ln a memoir 
on pectic acid and on carrots, by M. Vauquelin, 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 them 
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 than 
when caustic potash is employed. 
