QUESTIONS AND ANSWERS 41 



Define (a) osmosis, (b) diffusion. 



(a) Osmosis is the phenomenon of the passage of certain fluids 

 through a porous substance, usually an animal membrane. 



(b) Diffusion is the gradual interchange of the particles of mis- 

 cible liquids when brought together. 



CAEBOHYDEATES 



Define carbohydrates. How do they differ from hydrocarbons ? Give 

 an example of each. 

 Carbohydrates are organic compounds composed of hydrogen, 

 carbon and oxygen ; hydrogen and oxygen usually being present in 

 the same proportion as in water. Example : glucose, CsHj206. 



A hydrocarbon is an organic compound composed of carbon and 

 hydrogen. Example: methane, CH^. 



Mention carbohydrates that are common food for horses and cattle. 



Starches, sugars and gums which are present in large propor- 

 tions in nearly all the common feeding-stuffs. 



PATS 



Define fats. Give the names of three fats. 



Pats are compounds of the glyceryl radical and a fat acid 

 radical. They are formed by glycerine and a fat acid, and consist 

 of carbon, hydrogen and oxygen, are insoluble in water, slightly 

 soluble in cold alcohol, easily soluble in ether. In a pure state, 

 all fats are odorless, colorless, tasteless substances, and stain paper 

 permanently. 



Palmitin, stearin and olein are the principal animal fats. 



What is soap? Describe a laboratory method of preparing soap. 



Soap is a compound of one or more fatty acids with an alkali. 

 It is usually prepared by the direct action of caustic soda or 

 potash upon fats. 



MILK 



What is the composition of normal cow's milk? 



The average composition may be given as follows : 



Water 871.7 



Solids 128.3 



Albumins 35.5 



Fats 36.9 



Lactose 48.8 



Salts 7.1 



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