IN POPULAR CHEMISTRY. 83 



Each molecule of NaCl thus yields one molecule of HC1. 

 HC1 : NaCl : : 25 : x. 

 36.5 : 58.5 : : 25 : x. 

 x = 40 + , kilograms. 



5. HCl of a specific gravity of 1.2 contains about 4O 

 per cent, of the gas. This is very strong commercial acid. 

 What weight could be formed by the HCl gas produced in 

 the reaction named in the preceding problem ? 



25 kilos = .40 x. 

 x = ~= 62.5 kilos. 



4vJ 



f>. What is the difference betiveen sublimation and dis- 

 tillation ? 



A body is said to sublime when it rises as vapor and con- 

 denses in the solid form ; when it condenses as a liquid it is 

 said to distil. 



7. Why do eggs discolor silver spoons ? 



The sulphur of the egg combines with the Ag, forming 

 silver sulphide. 



8. Explain the principle of hair-dyes. 



The two principal chemicals used for dyeing the hair are 

 lead and silver nitrate. The S in the hair combining with the 

 Ag makes silver sulphide, or with the Pb, lead sulphide, either 

 of which stains the hair ; the former colors the skin as well as 

 the hair, while the latter is absorbed through the skin, causing 

 colics and other diseases such as are common among painters. 

 The "golden yellow color" lately in fashion is produced by a 

 solution of arsenic with the hydrosulphate of ammonia. In or- 

 der to dye the lighter tints, it is necessary to bleach the hair 

 with an alkaline solution. See Fireside Science, page 77. 



9. Ts 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. 



