204 farmers' and mechanics' journal. 



several pieces are to be soldered one to the other. The least fusi- 

 ble solder is employed in the first place ; and the other degrees in 

 proportion to the nunf)ber of pieces to be soldered. By adopting 

 this precaution, the first soldered pieces are not affected by the 

 degree of heat necessary for ioinins; the other pieces. 



Soft solder is a mixture of two parts of tin and one of lead, 

 poured into ingot-moulds. It is used with a hot iron, as the 

 plumbers and tinmen use it. 



Solders for Brass. — Two kinds of these solders are also em- 

 ployed ; the harrl and the soft. The hard is made in the same 

 manner as that for cooper, but of brass and zinc ; and the propor- 

 tions may be varied from 16 parts of brass and one of zinc, to two 

 parts of brass and one of zinc. 



The soft solder is made of six parts of brass, one of zinc, and 

 one of tin. The brass is first melted ; the tin is then added ; and, 

 lastly, the zinc ; which last metal should be first well heated. The 

 wbole is then agitated, and divided into grains, by the process 

 above explained. 



I' is always necessary, before soldorin?, to clean the surfaces 

 well, which are to be soldered, either wifh a file, a srraper. &c. 



[Diciionnaire Technulogiquc. 



To make a Silveriiig Poiiider^ to put a coat of Silver on Copper^ 

 when zoom off, 



Ta^ce of the drv muriate of silver, such as is procured when you 

 clear nitric acid from the muriatic acid ; or make it by dissolving 

 any small piece of common silver coin, such as a cjuarter dollar, in 

 nitric acid, and then adding to the solution common salt. By so 

 doing, the common salt is decomposed, the acid thereof unites to 

 the si'ver. and the alkali thereof to the nitric acid. Of this mu- 

 riate of s'lver dried in the shade, take by measure one part ; of 

 cream of tartar, three parts : of common salt, three parts ; of com- 

 mon wbiti'^iT. three parts. Mix all together, and when you want to 

 i-pnew the silver on copper, in places where it is worn off, rub a 

 little of this mixture by means of a moist rag on the abraded place ; 

 the silver wHl take the nlace of the Conner ; and it can be washed 

 and <^leaned. But it will not bear murb rubbing or scrubbing. It 

 is, howpver, a very convenient and useful receipt, particularly for 

 articles of plated ware, which can have the silvering renewed at a 

 verv trifling evnense. 



The rationale of this proeess is very complicated ; the super- 

 tartrite of potash, or the cream of tartar, and the muriate of silver 

 decompose each other : a ta'-fpite of lime is formed ; the excess of 

 acid is neutralized by the wbitins: forming a tartrite of lime, which 

 with the common salt, serves to clean the surface of the copper : 

 the tartrite of silver at the moment of its formation is decomposed 

 bv the conpcr or brass, and the silver is precipitated in a metallic 

 state on the copoer : it will admit of beinnr polished with the palm 

 of the hand, but is too thin to bear burnishing. 



