Dec. 1, 1804.1 THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 201 



whole to the boil by means of a jet of steam. Under the influence of 

 the alkali the tissues are swollen and dissolved and the fat liberated. 

 By these operations a better quality of fat is obtained and no nuisance 

 is created. It is found advantageous to purify or bleach the above fatty 

 matters by the following means. Mr. Dawson's process consists in 

 passing air through the melted tallow, and Mr. "Watson's in heating 

 melted fatty matter with permanganate of potash. Both these pro- 

 cesses are based on the oxydation of the colouring organic matter. 

 Some tallow-melters further clarify their tallow by adding 5 lbs. of 

 alum in powder to 100 lbs. of melted tallow, which separates and pre- 

 cipitates any colouring matter, The white snowy appearance of American 

 lard, which is rather deceptive to the eye than profitable, is obtained 

 by thoroughly mixing, by means of machinery, starch in a state of jelly 

 with a little alum and lime, with the fatty matter, by which means two 

 ends are attained — viz., the introduction of 25 per cent, of useless 

 matter, and a perfect whiteness from the high state of division of the 

 same. The fatty matters from fish are generally obtained by boiling 

 those parts of the fish containing them with water, when the fatty 

 matters rise to the surface of the fluid, and one whale has been known 

 to yield as much as 100 tons of oil. According to M. Chevreul, the com- 

 position of whale oil is as follows : — 



*■«*■ |Sf ie ' 



together with a small amount of colouring matter, and of phocenic acid, 

 which gives to whale oil its disagreeable colour and odour. Many 

 attempts have been made to sweeten whale oil by the use of weak 

 caustic lye, milk of lime, sulphuric acid, and steam ; but although a 

 great improvement has been effected, the oil is still recognisable by its 

 unpleasant odour. I have no doubt in my mind, from experiments 

 made by my friend Mr. Clift, that fish oils might be obtained as sweet 

 as vegetable oils, if proper means for its extraction were adopted. Allow 

 me here to revert to animal fats to show you that their comparative hard- 

 ness or solidity, as shown by the following table, depends upon their 

 relative proportions of stearine or margarine and oleine : — 





Stearine or 

 Margarine. 

 ... 75 



Oleine, 

 .... 25 .... 



Melting. 

 point. 



nro° 





... 74 



.... 25 .... 



109-0 





... 38 



.... 62 .... 



80-5 





) ... 40 



. . . . 60 



86-2 



Do. (winter) 



... 63 



.... 57 .... 



79-7 



... 32 



.... 68 .... 



79-0 





. 28 . 



72 



77-0 



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A A 



