294 BARYTA 



salt Barwood contains, therefore, 23 per cent, of red colouring-matter; whilst 

 saunders wood, according to Pelletier, only contains 16'75. 



The alcoholic solution behaves in the following manner towards reagents : 



Distilled water added in great quantity . Produces a considerable yellow opales- 



cence. The precipitate is re-dissolved 

 by the fixed alkalis, and the liquor ac- 

 quires a dark vinous colour. 



Fixed alkalis ..... Ttirn it dark crimson, or dark violet. 



Lime-water .....< Ditto. 



Sulphuric acid Darkens the colour to a cochineal red. 



Sulphuretted hydrogen .... Acts like water. 



Salt of tin Blood-red precipitate. 



Chloride of tin . . . . . Brick-red precipitate. 



Acetate of lead Dark violet gelatinous precipitate. 



Salts of the protoxide of iron . . Very abundant violet precipitates. 



Copper salts Violet-brown gelatinous precipitates. 



Chloride of mercury .... An abundant precipitate of a brick-red 



colour. 



Nitrate of bismuth .... Gives a light and brilliant crimson red. 



Sulphate of zinc . . . . Bright red flocculent precipitate. 



Tartar emetic . . . . .An abundant precipitate of a dark cherry 



colour. 



Neutral salts of potash .... Act like pure water. 



Water of baryta ..... Dark violet-brown precipitate. 



Gelatine ...... Brownish-yellow ochreous precipitate. 



Chlorine ...... Brings back the liquor to a light yellow, 



with a slight yellowish-brown precipitate, 

 resembling hydrated peroxide of iron. 



Pyroxylic spirit acts on barwood like alcohol, and the strongly coloured solution 

 behaves similarly towards reagents. Hydrated ether almost immediately acquires 

 an orange-red tint, rather paler than that with alcohol. It dissolves 19'47 per cent, of 

 the colouring-principle. Ammonia, potash, and soda, in contact with powdered barwood, 

 assume an extremely dark violet-red colour. These solutions, neutralised with hydro- 

 chloric acid, deposit the colouring-matter in the form of a dark reddish-brown powder. 

 Acetic acid becomes of a dark-red colour, as with saunders wood. 



Barwood is but slightly soluble ; but the difficulty arising from its slight solubility 

 is, according to Mr. Napier, overcome by the following very ingenious arrangement : 

 The colouring-matter while hot combines easily with the proto-compounds of tin, 

 forming an insoluble rich red colour. The goods to be dyed are impregnated with 

 proto-chloride of tin combined with sumach. The proper proportion of barwood for 

 the colour wanted is put into a boiler with water and brought to boil. The goods 

 thus impregnated are put into this boiling water containing the rasped wood, and 

 the small portion of colouring-matter dissolved in the water is immediately taken up 

 by the goods. The water, thus exhausted, dissolves a new portion of colouring- 

 matter, which is again taken up by the goods, and so on till the tin upon the cloth 

 has become (if wo may so term it) saturated. The colour is then at its brightest and 

 richest phase. 



BARYTA. (Baryte, Fr.) One of the simple earths, protoxide of barium (BaO). 

 It may be obtained most easily by dissolving the native carbonate of baryta in nitnc 

 acid, evaporating the neutral nitrate till crystals bo formed, draining and then cal- 

 cining these, by successive portions, in a covered platina crucible, at a bright red heat. 

 A less pure baryta may bo obtained by igniting strongly a mixture of the carbonate 

 and charcoal, both in fine powder and moistened. It is a greyish-white earthy 

 looking substance, fusible only at the jet of the oxy-hydrogcn blowpipe, has a sharp 

 caustic taste, corrodes the tongue and all animal matter, is poisonous even in small 

 quantities, has a very powerful alkaline reaction ; a specific gravity of 4'0 ; becomes 

 hot, and slakes violently when sprinkled with water, falling into a fine white powder, 

 called the hydrate of baryta, which contains 10 per cent, of water, and dissolves in 

 10 parts of boiling water. This solution lets fall abundant columnar crystals of 

 hydrate of baryta as it cools ; but it still retains one-twentieth its weight of baryta, 

 and is called baryta water. The above crystals contvin 61 percent, of water, of which, 

 by drying, they lose 50 parts. This hydrate may be fused at a red heat without 

 losing any more water. Of all the bases, baryta has the strongest affinity for sul- 

 phuric acid, and is hence employed either in the state of the above water, or in that 

 of one of its neutral salts, as the chloride to detect the presence and determine the 

 quantity of that acid present in any soluble compound. 



