ON THE COMPOSITION OF BIED-LIME. 21 



this is the best way of proceeding. It is, however, difficult to get 

 quite free from potash, and needs, to this end, to be repeatedly dis- 

 solved in ether and reprecipitated by alcohol. The caoutchouc can 

 also be separated by dissolving the bird-lime in ether and precipitat- 

 ing the solution with 95 ^/o spirit, but then only very imperfectly, 

 because the main constituent of the bird-lime also precipitates partly. 

 The caoutchouc of bird-lime is pale yellow and transparent, highly 

 elastic, and when heated evolves the well-known penetrating odour. 

 A combustion analysis of it gave us carbon 86.56, and hydrogen 

 11.31 per cent., so that oxygen to the extent of 2 per cent, was 

 present. Before weighing it out, it had been kept for some time at 

 120''- 130°. It left when burnt a trace of ash. 



Other and principal constituents ofhird-lime. — AVe have not fully 

 isolated these by proximate analytical methods, l)ut their general 

 properties appear to be those of the partially purified bird-lime. For 

 when a boiUng spirit-solution of bird-lime is evaporated and cooled, 

 and aii'ain when an ether-solution of bird-lime is mixed with a little 

 alcohol, to separate the caoutchouc, and then evaporated, in both cases 

 the solid matter obtained is quite like the partially purified bird-lime, 

 except in being without colour when deposited from the cooling 

 spirit solution. 



Products of the saponification of hird-Uine, and their isolation. — 

 Saponification with alcoholic potash yields, besides the residual caout- 

 chouc, firstly, the potassium salt of palmitic acid and a very little of 

 that of a semi-solid acid which we have been unable to purify or 

 identify ; secondly, tiro cnistalline alcohols ; and thirdly, a small 

 quantity of a resinoïd body. The separation of these bodies may be 

 carried out in somewhat different ways, and is unavoidably tedious. 

 The purified bird-lime is boiled for two hours with potash and 95 ^o 

 spirit, in a fiask fitted with a condenser ; the alkaline solution. 



