SEPARATION OF SOLIDS BY MEANS OF SOLVENTS. 71 



common table salt in powder and stir or shake ; the salt will 

 dissolve in the water, and the soap will separate in soft pasty 

 flakes. 



Expt. 66. To separate a Mixture of Sugar and Sand by 

 means of a Solvent. The property possessed by certain liquids of 

 readily dissolving substances which are almost insoluble in other 

 liquids is often made use of for the purpose of separating substances 

 when mixed together, not only in carrying out analytical opera- 

 tions in the laboratory, but also in various manufactures ; e.g., the 

 preparation of many kinds of dyeing materials. Sometimes sugar 

 is adulterated with sand ; such an admixture is easily recognised by 

 treating the mixture with hot water, when the sugar dissolves, 

 leaving the sand unaltered. 



Expt. 67. To separate Salt and Clay. In the same way 

 salt and dried clay or brick-dust may be separated. Mix a tea- 

 spoonful of each in a mortar, and then pour a cupful of warm 

 water on the powder. The salt will dissolve, whilst the brick- 

 dust will be unaltered. By filtering the fluid through a paper 

 filter supported by a funnel (Expt. 56), a clear solution of salt 

 will be obtained, in which the presence of salt may be recognised 

 by testing with nitrate of silver (Expt. 37), or by evaporating down 

 (Expt. 55). 



Expt. 68. To separate three Solids by two diiferent Solvents. 

 Take some camphor, a little of the blue salt termed sulphate 

 of copper, and some fine white sand, and rub the whole together 

 in a mortar until a uniform bluish powder is obtained. Put some 

 of this into a bottle with some strong alcohol, and cork the 

 bottle and shake it up a few times ; let the un dissolved matter 

 subside, and pour it off the clear spirit ; if not sufficiently clear it 

 may be passed through a paper filter (Expt. 56), and the clear 

 filtered liquid set aside in a basin ; by and by the spirit will evap- 

 orate, and the camphor will be left ; or water may be added to the 

 filtered spirit, when the camphor will be precipitated in crystals. 

 Repeat the treatment with alcohol once or twice, to make sure 

 that all the camphor is dissolved. Next pour some warm water 

 into the bottle and shake up ; allow to subside, and pour off the 

 bluish watery fluid, filtering it if not quite clear; pour more 

 water into the bottle, and repeat the process until the water no 

 longer takes any blue colour. You will now have the sand just 

 as at first, wholly undissolved by either of the two solvents suc- 

 cessively applied; the camphor has been dissolved out by the first 

 treatment with spirit, and the sulphate of copper is obtained in the 

 solid form by evaporating down the blue watery solution until 

 the water is driven off". 



