244 SCIENTIFIC AMUSEMENTS. 



accordingly the use of animal charcoal for clarifying syrups in the 

 manufacture of refined sugar is an important part of that trade. 



Expt. 289. To Decolorise Beer, &c., by Animal Charcoal. 

 The colour of ordinary beer and porter is mostly due to the 

 presence of substances formed by the action of heat on sugar 

 during the preparation of the malt, &c., just as " Caramel " or 

 burnt sugar is employed by cooks for browning gravies, sauces, 

 and the like. Get a pint of dark coloured beer ; put into it an 

 ounce of finely powdered good animal charcoal, and boil the whole 

 for a few minutes in a flask ; or in a distilling arrangement 

 (Expt. 38) if it is wanted to save the spirit evaporated during the 

 boiling. Pour the turbid black fluid on to a large paper filter 

 (Expt. 56) supported by a glass funnel, and you will shortly see 

 that the clear fluid that filters through the paper is either colour- 

 less, or at least very much paler than the original beer, showing 

 that the charcoal has absorbed most of the colouring matter. By 

 boiling for a longer time, adding distilled water as the fluid 

 evaporates, you can generally succeed in getting a filtrate nearly 

 as white as water from an ordinary beer of only moderately dark 

 tint ; with stout or porter the lightening in tint is relatively still 

 more marked, although actually the filtered liquid will usually be 

 somewhat more coloured than that from a lighter ale. 



In the refining of sugar the coarse raw brown sugar is dissolved 

 in boiling water and treated with charcoal, whereby the syrup is 

 rendered almost colourless, so that when evaporated down it 

 ultimately forms crystallised sugar in the form of sugar loaves, 

 &c. Precisely the same kind of operation is resorted to in the 

 extraction and purification of many drugs and useful substances 

 extracted from vegetables and other products. Precipitated 

 sulphide of lead (Expt. 158) and many other substances possess 

 the same property to a less extent. 



Expt. 290. To dye Wool and Silk various Colours. 

 Animal fibres, such as woollen cloth and silk, possess the properties 

 of absorbing and combining with various kinds of colouring 

 matters either prepared from natural sources (vegetable like 

 indigo and madder derived from certain plants, or animal like 

 cochineal obtained from a kind of insect), or manufactured 

 artificially by somewhat complex chemical processes from materials 

 generally obtained in the first instance from coal tar, this being a 

 cheap source of the main ingredients. All animal fibres contain 

 nitrogen as one of the constituents, a fact easily proved by the 

 test described in Expt. 203 ; the presence of this nitrogen seems 

 to be connected with the power possessed by such fabrics of 

 absorbing colouring matters and becoming dyed or tinted there- 



