TINNING, PLATING, &C. S21 



heat. These were all the tracts which were published during th 

 life-time of Boerhaate ; he died in S ptembnr, 1738, and IP t Ins 

 papers to his two brothers, and after their deaths th'-y fell into the 

 hands of Charles Frederic Krusr, physician to the Empress of 

 Russia; this gentleman hath published a short extract from Boer- 

 haave's Diary, and promise's a fuller account of still more labo. 







rious operations. We learn from this extract*, that Boerhaave 

 had distilled the same mercury 1. '09 times, and its specific gravity 

 was to that of water, as 13 ^3 to I ; whilst that which had been 

 but once distilled was as 13 T Vo t-> 1 ; a difference which may ea- 

 sily b< attributed to the different temperatures of the air when the 

 experiments were made, or to other accidental circumstances, 

 which the accuracy of Gravesande, with whom he made the expe- 

 rim( nt, could not provide against. 



The mixture of quicksilver with gold, or silver, or lead, or tin, 

 or copper, or any metallic substance with which it is capable of 

 uniting, is called an amalgam ; and the operation by which the 

 union is effected, is called amalgamation. Authors are not agreed 

 as to the derivation of the word amalgam; some think that it is 

 composed of two Greek words, (aaa ya^eiv), by which the inti- 

 mate union, or marriage, as it were, of the two metals is denoted ; 

 others are of opinion, that it ought to be written a malagma, and 

 that it is derived from a Greek word (jH,aAa<r<ra;) signifying to 

 soften, inasmuch as the metal, be it what it may, is always soft, 

 ened by its union with the mercury. An amalgam, made of four 

 parts of tin and one of quicksilver, in the form of a ball, is used by 

 some under the pretence of purifying water ; it cannot, 1 think, 

 contribute in any manner to that end ; but as the ball is always 

 boiled in the water, the seeds of vegetables, or the tish spawn, or 

 the animalcules, &c. with which water is often polluted, may be 

 precipitated by the action of boiling. But there is another pur- 

 pose to which a mixture of tin and quicksilver is applied with great 

 utility the silvering of looking-glasses. 



Tin may be beat out into leaves not thicker than paper, called 

 foils ; on tin-foil, fitly disposed on a flat table, quicksilver is 

 poured, and gently rubbed with a hare's foot ; it sooi .1 t-s itself 

 with the tin, which then becomes very splendid, or, a> iliu work- 

 men say, is quickened : a plate of glass is then cautiously slid 



Novi Cummm. Pctrop. torn. ix. 

 VOt. TI. Y 



