134 AN8WEBS TO PRACTICAL QUESTIONS 



7. Why do beans, rice, etc., swell when cooked'} 

 By the bursting of the starch granules. 



8. Why does decaying wood darken ? 



By the formation of humus which contains carbon in 

 excess. 



9. Why does smoke cure hams ? 



The creosote of the smoke has powerful antiseptic 

 properties. 



10. How would you show that C exists in sugar 1 } 



By the experiments described in the Chemistry on page 

 117, note ; page 190, note ; and page 191 in the formation 

 of caramel. 



1 1. Why do fruits lose their sweetness when over-ripe ? 



(See Miller's Organic Chemistry, page 875.) 



The vegetable acid contained in the fruit when green, 

 oxidizes as the ripening process continues, O being ab- 

 sorbed and CO 2 evolved. If this continues too long, the 

 sugar itself becomes oxidized. 



12. Why does maple-sap lose its sweetness when the leaf 

 starts ? 



The sugar of the sap is applied to the wants of the 

 growing tree. 



13. Should yeast-cakes be allowed to freeze ? 

 A cold of 32 will kill the ferment. 



