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Chemical Science. 405 



in which it can be dissolved and from which it crystallises on cooling. So far 

 back as 1861 an editorial article in the " Chemical News " contains the following 

 passage: — "Hot aniline dissolves indigo, forming a solution having almost 

 exactly the tint of the solution of azuline in methylated spirit. On cooling, 

 the indigo crystallises out in beautiful coppery spangles. This method 

 of crystallising indigo from a solution in boiling aniline does not appear to be 

 generally known to chemists." Dr. V. Wartha now states that Venetian tur- 

 pentine, heated to its incipient boiling-point, is a solvent for indigo, which, 

 after cooling, is readily purified by the aid of ether or alcohol. Boiling 

 paraffin also dissolves indigo-blue, and the paraffin can be removed, after 

 cooling, by means of benzol. Spermaceti, stearic acid, and chloroform, all at 

 a high temperature, are stated to be more or less good solvents for indigo. 



According to the German chemist Kopp, a mixture of two liquids boils at a 

 lower temperature than either of the component liquids separately. Mr. D. 

 Howard has verified this law in the case of a mixture of amylic alcohol and 

 water, which boils at a lower degree than pure water. 



M. A. Valenciennes, of the chemical works at St. Denis, near Paris, has 

 lately prepared metallic manganese and several of its alloys. The metal was 

 obtained by the reduction of pure binoxide of manganese in a magnesia 

 crucible, and formed a brittle and very hard button. Immediately after break- 

 ing it, the pieces were as white as cast-iron, but more rapidly oxidised by the 

 air. Manganese shows great affinity for copper. Valenciennes prepared 

 alloys of copper and manganese, containing from 3 to 20 per cent of man- 

 ganese, all of which resemble very much the copper-tin alloys (bronzes), 

 being, like these, hard, sonorous, and easily fusible. The alloy, containing 15 

 per cent of manganese, is grey, very hard, brittle, fuses like bronze, is 

 easily cast into moulds, and remains unchanged for some time. The alloy 

 with 12 per cent of manganese is also brittle and very hard, grey after 

 being turned, but soon becomes yellow as brass. 



A cold solution of bichromate of potassa in nitric acid is, according to Dr. 

 Bottger, an excellent test for the genuineness of silver plating on metals. The 

 metallic surface to be tested is first of all cleaned with strong alcohol, in order 

 to remove dirt, fatty matter, and especially any varnish. A drop of the 

 test fluid is then applied to the metallic surface by means of a glass rod, 

 and immediately afterwards washed off with some cold water. If pure silver 

 is present, there will appear a blood-red coloured mark (chromate of silver). 

 Upon German silver the test liquid appears brown, but after washing with 

 water the blood-red coloured mark does not appear ; the so-called Britannia- 

 metal is coloured black ; on platinum no action is visible ; metallic surfaces 

 coated with an amalgam of mercury yield a reddish speck, which, however, 

 is entirely washed off by water ; on lead and bismuth the test liquid forms a 

 yellow-coloured precipitate ; zinc and tin are both strongly acted upon by this 

 test liquid ; the stain as regards the former metal is entirely removed by 

 water, while, as regards the latter, the test liquid is coloured brownish, 

 and addition of water produces a yellow precipitate which somewhat adheres 

 to the tin. 



A method of imparting a yellowish hue to white marble is sometimes 

 wanted. Dr. R. Weber has made known the fact that alcoholic solutions 

 of perchoride of iron are not precipitated by carbonate of lime, and may 

 therefore be applied in different degrees of concentration to impart a more 

 or less deep yellow hue to white marble. The converse of this — the removal 

 of yellow stains from white marble — is still a desideratum. 



In experimenting upon the mother-liquors of the manufacture of sulphate of 

 quinine, Mr. D. Howard has occasionally been perplexed by an unusual 

 loss in re-crystallising, which the mechanically adhering mother-liquor did 

 not seem to account for. A more careful examination showed that the cause 

 was the presence of an alkaloid hitherto undescribed, the extreme solubility of 

 the salts of which both distinguishes it at once from the chinchona alkaloids 

 already known, and renders it very difficult to separate from the uncrystal- 



