LUBRICATING OIL. 159 



manner as follows. Transfer the green chrome liquor, after 

 the separation of the fat, to a tub, dilute it with water, and 

 then add thick milk of lime until the sulphuric acid is nearly 

 saturated ; leave to repose, decant the liquor from the sulphate 

 of lime, and carefully add to it another portion of cream of 

 lime until the precipitation of all the green oxide, and the 

 supernatant liquor is clear and colorless. Drain off this 

 liquor, add fresh water, and, after settling, again decant. 

 Repeat this washing, then transfer the precipitate to a red-hot 

 iron slab, and keep it constantly stirred until it changes to a 

 yellow powder. The chromate of lime, thus formed, if de- 

 composed by sulphuric acid in slight excess, yields chromic 

 acid as well suited for bleaching purposes as that from bi- 

 chromate of potassa. 



Oil-filter. — A good filter is said to be made of fine sand, 

 charcoal, and gypsum ; the sand to retain substances sus- 

 pended in it, charcoal to decolorize it, and plaster to remove 

 water. (Journ. de Chim. Med. 1846.) 



Ratv Linseed Oil Decolorized. — A solution of 2i]b copperas 

 in 2|ft) water is poured into a flask containing 2ib linseed oil, 

 and exposed to the sun for several weeks, during which it is 

 frequently shaken. The oil is said to be rendered limpid and 

 colorless, and may be drawn ofi" by a siphon or stoppered 

 funnel. 



Lubricating Oil. — Many substitutes have been proposed for 

 the more costly oil for lubricating machinery, but hitherto 

 with only partial success. Munkittrick's patent (Lend. Journ. 

 xxxvi. 98) consists mainly in the addition of caoutchouc to 

 common grease, the former being softened by spirit of terpen- 

 tine ; but he also uses other ingredients. For example : 10 

 galls, water being heated, lib glue and lOib carbonate of soda 

 are stirred in, 10 galls, oil or grease are next added, whereby 

 a quasi soap is formed, and lastly, 4}]b caoutchouc, softened by 

 terpentine, are incorporated. 



Boudet (Journ. de Pharm., and Lond. Pharm. Journ. 1850), 

 gives the following as the process by which the French Hard., 

 or lubricating fluid, is made. Add 1 pt. finely minced caout- 



