On the EffeEl of a Mixture of Tin with Gold, 1 8l 



does not poflefs its ufual duclility, particularly when it Is laminated very thin without re- 

 peated annealing as the metal becomes hard. 



It might be prefumed, in refleding on the experiment I have related, that the frafture 

 of the pieces of gold was owing to an incomplete fufion or unequal mixture of the two me- 

 tals. I was aware, from this notion, that it was proper to melt the ingot over again with 

 all the parts which had been feparated from it, and to negleft no precaution, after well 

 mixing it, that it fhould be poured out in perfedl fufion. At the moment this ftate of fu- 

 fion was obtained, I threw a fmall quantity of calcined borax upon the metal. In order that 

 its furface might become clear, and every foreign fubftance might be carried to the circum- 

 ference. No other confequence could arife from this ufe of borax than a greater foftnefs 

 in the compound, and confequently lefs rifk of its breaking when it came to be fubjefted to 

 the hammer. 



All my precautions were ufelefs. I forged one end, which was lengthened very well 

 without any perceptible crack ; but the extremity of this ingot, afterwards reduced to a 

 fmall thicknefs and expofed to the annealing heat, became divided into feveral parts, the 

 longed of which was contorted, and would no doubt have broken If the heat had been 

 ftronger, or continued for a greater length of time. 



Though the experiment, of which I have related the refult, on the mixture of one part of 

 tin and 24 parts of gold of 22 carats, might, In ftriclnefs, have been fufficient to prove that 

 this alloy deprives gold of great part of its dudlility, and expofes it, while annealing, to an 

 accident which artifts would fcarcely be able to avoid, from the neceflity they are under of 

 ' continually reftoring the malleability of the gold they work, by annealing It after it has be- 

 come hard under the hammer ; I neverthelefs thought it proper to lay afide the objedlion I 

 had to deprive my fine gold of its dudlillty, which could not be reflored but by a new part- 

 ing eflay, and to repeat the experiment by ufing gold of 24 carats In fuch a quantity that 

 my operation might be compared with that of Mr. Alchorne, from which chiefly he has 

 drawn his conclufion. 



I therefore employed 6 ounces of fine gold and 2 gros of tin for this new experiment. 

 The firft of thefe metals was divided into a great number of pieces, and I had Included the 

 two gros of tin in two leaves of gold taken from the 6 ounces, rolled out very thin, and fo 

 flexible, after arinealing, that they perfectly enveloped the tin. After having put one part 

 •f the gold at the bottom of a fmall crucible, I placed the tin wrapped up in gold upon it, 

 and over this I put the remainder of the gold. 



When the whole of the two metals was In perfeft fufion, I poured them fpcedily into 

 an ingot mould, which I had before ufed, and obtained an ingot rather longer and cleaner 

 than the two former. 



As foon as It was cold, I forged one of Its extremities with the edge of the hammer^ 

 It was lengthened without any perceptible crack; and when it was reduced to the thicknefs 

 of one line, or thereabouts,! cut it off for feparate treatment. By moderate annealing It main- 

 tained its integrity; and, with the exception of a few cracks, it paffed the laminating 

 rollers without breaking. As I was fearful, neverthelefs, that it might break in fome part if 

 I continued to laminate it, I gave it a flight annealing. It had fcarcely acquired a cherry 

 rcdnefs between the charcoal before it broke into five or fix parts, fome of which were 

 fimply bended or twilled, and others flat as they quitted the rollers. Among the annealed 



6 pieces 



