42O 



SCIENTIFIC RECREATIONS. 

 COMPARATIVE TABLE OF HYDROMETERS. 



Chloroform is transparent, and will sink in water. Diluted alcohol 

 with hypo-chloride of lime, will produce it. When inhaled, chloroform pro- 

 duces a pleasing insensibility to pain, and is useful in surgery. 



A certain compound of alcohol with mercury dissolved in nitric acid 

 will cause decomposition, and white crystals will eventuate. These compound 

 crystals are termed fulminating mercury. 



We must now pass rapidly over the few remaining subjects we have to 

 notice, such as fats and soaps, wax, oils, etc. 



Fats are of the greatest use to man, particularly in cold climates, for upon 

 them depends the heat of the body. Fatty acid, if liquid, is known as oleic 

 acid ; if solid, stearic acid. Soaps are compounds of fatty acids. Many 

 "fats" are consumed as food, others as fuel or for lighting purposes, in the 

 shape of oils. Such oils are not primarily useful for burning. Petroleum- 

 and other mineral oils are found in enormous quantities in America. 



There are what we term fixed oils, and essential or volatile oils. A 

 list is annexed as given by " Hadyn's Dictionary of Science " : 



FIXED OILS. 



Drying. 

 Linseed oil. 

 Poppy oil. 

 Sunflower oil 

 Walnut oil. 

 Tobacco-seed oil. 

 Cress-seed oil. 



Non-Drying. 

 Almond oil. 

 Castor oil. 

 Colza oil. 

 Oil of mustard. 

 Rape-seed oil. 

 Olive oil, etc. 



