IN POPULAR CHEMISTRY. 105 



25. How does a bird obtain the CaCO 3 for its egg 



shells ? 



(See chemistry of a lien's egg in Fireside Science.) 



A common hen's egg is 95 per cent, carbonate of lime, one 

 per cent, phosphate of lime and magnesia, and two per cent, 

 animal matter. The shell would weigh over 100 grains, so that 

 a hen laying 100 eggs in a season would require nearly 1^ Ibs. 

 of CaCO 3 . The hen must in part secrete this from her food, 

 and in part gather it from the sand, pebbles, etc., she picks up 

 amid her incessant scratching and searching. 



26. Why does new soap act on the hands more than 

 old ? 



The spent lye, which contains the excess of alkali, gradu- 

 ally separates from the soap, leaving only the salts in which 

 the alkali is neutralized by the fatty acids. Also a more com- 

 plete combination takes place, whereby some free alkali is 

 taken up by the acids, perhaps before uncombined. The for- 

 mer statement is especially true in the case of soft or home- 

 made soap. 



27. What is the shiny coat on certain leaves and fruits ? 



A species of wax secreted by the plant. 



28. Why does tiwpentine burn with so much, smoke ? 



Because it contains an excess of carbon. 



20. Wliy is the nozzle of a turpentine bottle so sticky ? 



The turpentine on exposure to the air oxidizes, turning to 

 rosin. 



30. Why does kerosene give more light than alcohol ? 



It contains more carbon, which, when heated in the flame 

 of the burning H, gives out a white light. 



31. IVliat is the antidote to oxalic acid ? Why ? 



Magnesia or chalk, forming an insoluble oxalate. 



32. Would you iveaken camphor spirits with ivater ? 



