IN CHEMISTRY. 87 



2. What is the difference between an -ate, an -ite, and an 

 -ide compound? 



An -ate compound is a union of an -ic acid with a base ; 

 an -ite compound is a union of an -ous acid with a base; 

 and an -ide compound is a union of two elements, a 

 binary compound. EXAMPLES. Iron sulphate, FeSO 4 ; 

 calcium sulphite, CaSO 3 ; potassium chloride, KC1. 



3. Why does not canned fruit decay ? 

 Because the O of the air is excluded. 



4. Where is the higher oxide formed, at the forge or in 

 the pantry ? 



(See Chemistry, page 33, note.) 



5. Why is the blood red in the arteries and dark in the 

 veins ? 



When specimens of venous and of arterial blood are 

 subjected to chemical examination, the differences pre- 

 sented by their solid and fluid constituents are found to 

 be very small and inconstant. As a rule, there is rather 

 more water in arterial blood, and rather more fatty mat- 

 ter. But the gaseous contents of the two kinds of blood 

 differ widely in the proportion which the carbonic acid 

 gas bears to the oxygen ; there being a smaller quantity 

 of oxygen and a greater quantity of carbonic acid, in 

 venous than in arterial blood. And it may be experi- 

 mentally demonstrated that this difference in their gaseous 

 contents is the only essential difference between venous 

 and arterial blood. For if arterial blood be shaken up 

 with carbonic acid, so as to be thoroughly saturated with 

 that gas, it loses oxygen, gains carbonic acid, and acquires 

 the hue and properties of venous blood ; while, if venous 



