106 ANSWERS TO PRACTICAL QUESTIONS. 



No ; since camphor is insoluble in dilute alcohol. The prin- 

 ciple is the same as that of the precipitation of lead from 

 dilute sulphuric acid. 



35. What is the difference between rosin and resin ? 



Rosin is an oxidized resin. Rosin is a species, and resin a 

 genus. 



34. IVJiy does skim -milk look blue and new milk 

 white ? 



The globules of butter contained in new milk reflect the 

 light, and so make it look white ; but when they are removed, 

 by the separation of the cream, more light is transmitted, and 

 only the blue is reflected to the eye. 



35. Wliy does an ink-spot turn yellow after washing 

 with soap ? 



The free alkali of the soap combines with the tannic acid 

 of the ink, leaving the oxide of iron (ferric oxide), which stains 

 the cloth yellow. 



