176 



MAGISTRAL 



mitted to fermentation or else washed with a solution of sulphate of soda, is treated 

 with ten times its weight of a boiling solution of alum, containing one part of alum, 

 for fifteen or twenty minutes. The filtered liquid is mixed, as soon as its tempera- 

 ture has fallen to about 100 F., with a solution of carbonate of soda containing one- 

 eighth or one-tenth of the weight of the alum employed. This quantity is insuf- 

 ficient to cause any precipitate at that temperature, but on boiling the liquid, the lake 

 falls down in the shape of a red powder. The madder must be treated several times 

 with boiling alum-liquor, in order to extract the whole of the colouring-matter soluble 

 in that menstruum. It is evident that these lakes contain chiefly puipurine and very 

 little alizarine, the latter being hardly soluble in alum-liquor. See LAKE. 



Imports of Madder. 



MAGDAIiA RED. A name applied to naphthaline red. 



MAGENTA. A full description of this and analogous colours will be found under 

 ANILINE RED. We extract the following from Mr. Crookes's ' Handbook of Dyeing and 

 Calico-Printing ' : 



' The simplest method of testing a commercial sample of magenta both for intensity 

 and for purity of tone, is to dissolve a known weight in boiling water and to dye with 

 the strained decoction a known weight of fine white woollen yarn or cloth. By thus 

 comparing different samples, their respective tinctorial power can be readily ascer- 

 tained, and the presence of tarry matters, unconverted aniline, &c., may be detected 

 by the flatness and brownish cast of the colour. Sugar is sometimes used as an adul- 

 terant. This may be detected by treating the sample with concentrated alcohol. The 

 magenta dissolves and is filtered off", whilst the sugar remains behind undissolred. 



' The following method is used to ascertain whether a magenta is a pure salt of 

 rosaniline, or is contaminated with mauvaniline, violaniline, chrysotoluidine, &c. The 

 colour is dissolved in as little alcohol as possible, the solution diluted with its own 

 bulk of water or rather more, and a drop is taken up by means of a glass rod, and 

 applied to a piece of white blotting-paper. If more than one colouring-matter is 

 present, the different shades will diffuse themselves in concentric circles, and may be 

 distinctly seen. This method is still more applicable to the aniline violets and blues, 

 which are frequently heterogeneous. 



'Aniline Crimson. The crude magenta-cake, without any purification, is sold under 

 this name, and is used in dyeing certain maroons, browns, clarets, and other compound 

 colours. 



The colour well bruised or broken up into powder, is placed in a suitable stoneware 

 vessel and well stirred up with its own weight of hydrochloric acid. During this 

 process the fumes given off should be carefully avoided. After the colour has steeped 

 for a short time in the acid, boiling water is added sufficient to dissolve the whole. 

 The solution thus obtained is carefully strained, and is then ready for use. To correct 

 the acidity of the colour, a small quantity of ammonia is added to the dye-bath. This 

 preparation will in many cases supersede peachwood, producing brighter shades, with 

 less trouble, and at a lower price. They are, however, more fugitive. Upon wool 

 and silk, aniline crimson, like magenta, is a substantive colour. Upon vegetable 

 fibres it requires to be fixed with a mordant generally a per-salt of tin and an 

 astringent.' 



IVXAGXXiP. A vehicle used by artists, of a gelatinous character. Much secresy 

 prevails as to the manufacture of magilp. It appears to be essentially linseed-oil 

 which has been exposed for some time to the oxidising influences of the air, mixed 

 with good mastic varnish. 



iviAGISTERY is an old chemical term to designate white pulverulent substances, 

 spontaneously precipitated in making certain metallic solutions ; as magistery of 

 bismuth. 



MAGISTRAL, in the language of the Spanish smelters of Mexico and South 

 America, is the roasted and pulverised copper pyrites, which is added to the ground 

 ores of silver in their torta, or amalgamation-magma in the patio process for the 



