IN CHEMISTRY. 113 



15. How much O and H 2 O are needed to change a ton 

 of SO 2 /*H 8 SO 4 ? 



One ton of SO 2 will make if tons of H 2 SO 4 : of 

 which -fa is H, Jf is S, and f is O. i of this O, or ^ 

 comes from the air, and i = ^ ^ rom ^ e water - (See pro- 

 cess of manufacture, Chemistry, p. 116.) Hence -fa (O) 

 an d j^. (H) = - of the acid was furnished by the water 

 -fs of i-y- tons = -^g- ton (H 2 O). The process of reason- 

 ing may be seen more clearly, perhaps, by preparing the 

 formulae as in Question 18, page 99, of this Key. 



1 6. How much O in a Ib. <?/~H 2 SO 4 ? 



f f- of any quantity of sulphuric acid are O ; -fa is 

 H ; and f are S. Hence in i Ib. of H 2 SO 2 there are 



17. State the analogy between the compounds qfO and S. 



o 



H a O 



H 2 O 2 (hydrogen dioxide) 



C0 3 



S 



H 2 S 



H 2 S a 



CS 2 



The corresponding compounds possess not only an an- 

 alogous composition, but also similar chemical proper- 

 ties. 



146. i. In the experiment with Na 2 SO 4 , on page 133, 

 an accurate thermometer will show that in making the solu- 

 tion^ the temperature of the liquid will fall, and in its solidi- 

 fication, will rise. Explain. 



(See Philosophy, page 233.) 



The solid salt passing into a liquid takes up heat, 

 and, in returning from a liquid to a solid again, gives 

 up heat. The latter is illustrated in next question. 



