Il8 ANSWERS TO PRACTICAL QUESTIONS 



14. Will the burning phosphorus ignite the wood of the 

 match ? 



It does not give off enough heat in its oxidation to 

 raise the temperature of the wood to the igniting point. 

 Many, however, claim the true reason to be that, in burn- 

 ing, it produces an ash (P 2 O 5 ) which covers the wood as 

 with a varnish and so protects it from oxidation. 



15. What philosophical principle is illustrated in the 

 ignition of a match by friction ? 



(See Philosophy, page 230.) 



The conversion of motion into heat. 



1 6. How much H 2 O would be required to dissolve a 

 pound of "KNO 3 ? 



3 Ibs. of cold water and \ Ib. of hot water. 



17. What causes the bad odor after the discharge of a 

 gun? 



The potassium sulphide gradually gives up its S to 

 form HgS. 



1 8. Write in parallel columns the properties of common 

 and of red phosphorus. 



units of soda and one of water, which is sufficiently alkaline to promote 

 oxidation, dissolve albumen, and absorb carbonic acid, and yet holds the lat- 

 ter so loosely, that it instantly exchanges it for oxygen when it encounters 

 that gas in the pulmonary capillaries. Again, the flesh juice must be kept 

 acid (perhaps in opposition to the alkaline blood, as affecting the transmission 

 of the electric currents which traverse the tissues), and phosphoric acid pro- 

 vides a salt, containing two units of water and one of potash, which secures 

 the requisite acidity." DR. G. WILSON, Edinburgh Essays, 1856. 



