560 A.NNUAL RECORD OF SCIENCE AND INDUSTRY. 



transferred to the plating bath, and the proper amount of 

 metal is deposited upon them in the usual way. 



The peculiar stage of the process consists in submitting 

 the articles to the operation of firing. For this a bright red 

 heat is commonly employed, at least for articles that do not 

 require tempering. For cutting instruments the heat is more 

 carefully watched, and not allowed to rise above 450 or 500 

 Fahr. When the articles have attained a proper tempera- 

 ture, they are withdrawn, and instantly quenched in cold 

 water. 21 A^ JVovember, 1872, 1045. 



TESTS FOR GILDING. 



According to P. Geyot, if a gilt surface be touched with a 

 drop of chloride of gold or nitrate of silver solution, the 

 former will produce a brown, the latter a gray spot, if the 

 coating be an alloy, but will have no eifect upon pure gold. 

 For gilt paper, moisten with a drop of chloride of sulphur, 

 which will immediately produce a dark-brown margin, if the 

 covering is not pure gold. Metallic spangles, shaken in closed 

 flasks with chloride of sulphur, suffer no change, if gold, oth- 

 erwise they gradually darken; while under a slight pressure, 

 as in hermetically sealed tubes, gold spangles disappear in a 

 short time by conversion into chloride of gold. 13 C, De- 

 cember 15, 1872, 1624. 



COATING FIBRES WITH SILVER. 



A new industry has lately sprung up in England, which 

 has already attained considerable development, namely, the 

 silvering of any given animal, vegetable, or mineral sub- 

 stance for ornamental purposes. For this purpose two solu- 

 tions are necessary : the first, composed of quicklime, two 

 parts ; grape-sugar or honey, five parts ; tartaric acid (or, for 

 want of this, gallic acid), two parts; and water, 650 parts. 

 This is to be filtered, and the solution placed in bottles, to 

 be entirely filled and thoroughly sealed, so as to prevent any 

 action of the air. For the second solution, twenty parts of 

 nitrate of silver are to be dissolved in twenty parts of ammo- 

 nia, and the solution diluted with 650 parts of distilled water. 

 At the moment of using, the two liquids are to be mixed in 

 equal parts, and shaken carefully togetlier, and then filtered. 

 To silver wood, silk, hair, wool, or flax, or other fibres, they 



