LIME AND CEMENT INDUSTRIES 6 GO 



Milk of lime 



Frasch states that the slaking of lime is mostly done in wooden 

 boxes. For industrial purposes, where the lime is used in the 

 form of milk, as in the distillation of ammonia, mechanical 

 devices are employed for this purpose. The amount of lime 

 present in milk of lime of different density is given in the above 

 table from page 406, vol. 7 of Mineral industry, 



Scap 



In the manufacture of soap slaked lime is mixed with carbonate 

 of soda to produce caustic soda. The two are mixed with water, 

 and boiled with steam, the resulting carbonate of lime being 

 separated by settling. 1 



Lime is also used in the manufacture of soft soap, in that the 

 pearl ash of commerce is converted into caustic potash by means 

 of fresh lime. In the manufacture of stearin for candles ordi- 

 nary tallow is boiled in wooden vats by high pressure steam with 

 slaked lime for several hours, by which lime soap is formed. 

 This is transferred to another vessel and treated with dilute 

 sulfuric acid, which in combining with the lime forms a sulfate, 

 which deposits while the fatty acids rise to the surface. 2 



In the manufacture of ball soda or black ash, salt cake, lime- 

 stone and coal are mixed together in a reverberatory furnace. 

 The limestone is sometimes soft and chalk-like. Good limestone 

 should have 08$ of carbonate of lime. 3 



Palm oils and tallow are the two chief fats bleached by the 

 soapmaker. The color of the latter is sometimes removed by 

 boiling it in lead-lined tanks with a solution of chlorid of lime. 



In the saponification of tallow the latter is mixed with good 

 slaked lime into a thin cream with water. This is then inclosed 

 in a suitable vessel, and the whole boiled with steam and agitated 

 for three hours. The action of the lime on the tallow decom- 

 poses it, glycerin being set free, while calcium stearate and oleate 



i Watt- Art of soap-making, p. 128. 



2 " " p. 84. 



3 " " p. 109. 



