112 ANSWERS TO PRACTICAL QUESTIONS 



9. Why is new flannel apt to turn yellow when washed ? 



New flannels, washed in strong soap, turn yellow, be- 

 cause the alkali of the soap unites with the SO 2 used in 

 bleaching the cloth, and thus sets free the original color. 



10. Is it safe to mix oil of vitriol and water in a glass 

 bottle ? 



The heat produced by the combination of the two will 

 be liable to break the glass. 



11. What is the color of a sulphuric acid stain on cloth ? 

 How would you remove it? 



It is generally red, especially on black cloth. The 

 color may be restored by a few drops of a solution of 

 common "soda." 



12. What causes the milky look when oil of vitriol and 

 water are mixed ? 



Pb from the stills in which the acid is condensed, and 

 which is soluble in strong H 2 SO 4 , is precipitated when 

 the acid is diluted with H S O. 



13. What is the relation between animals and plants ? 

 Which perform the office of reduction, and which that of 



oxidation ? 



(See AVy, page 52, Question 19.) 



14. How many pounds of S are contained in 100 Ibs. of 

 H 2 SO 4 ? 



S : H 2 SO 4 : : x : 100 Ibs. 

 32 : 98 : : x : 100 Ibs. 

 98 x = 3200 Ibs. 

 x = 32-Jf Ibs. (S). 



