PLIABLE EGGS AND BONES. 215 



touched with a hot wire and is just beginning to burn ; if the 

 phosphorus has not begun to burn too vigorously, it will be extin- 

 guished. Now withdraw the spoon and relight the phosphorus 

 by holding it in a flame for an instant or two, and when it is well 

 alight introduce it again into the jar ; if burning vigorously when 

 introduced it will keep alight, but will not burn as freely as it 

 does in nitrous oxide (Expt. 250). The reason for this is that 

 whilst nitric oxide, like nitrous oxide, is a compound of nitrogen 

 and oxygen, it is not decomposed by heat so readily as the latter, 

 so that unless the phosphorus flame is hot enough to decompose 

 it, no oxygen is set free to feed the flame, which consequently 

 dies out. If, however, the heat be sufficient, the nitric oxide 

 becomes split up into nitrogen and oxygen, and the latter gas 

 keeps the phosphorus burning just as with nitrous oxide. 



Expt. 252. To get an Egg inside a Bottle. The brittle shell 

 of an egg chiefly consists of animal membrane with carbonate of 

 lime forming a thickening and strengthening solid mineral deposit 

 thereon ; by soaking an egg in dilute hydrochloric acid, the same 

 action is produced on the carbonate of lime as on the chalk in 

 Expts. 99 and 100 ; i.e., a double decomposition first takes place 

 between the carbonate of lime and hydrochloric acid, followed by 

 another action, the result of which is ultimately that chloride of 

 calcium is formed together with water, whilst carbon dioxide gas is 

 evolved. The effect of this is that the mineral matter is dissolved 

 away whilst the animal membrane is left soft and pliable ; in this 

 condition by careful manipulation the egg can be squeezed through 

 the neck of a bottle far narrower than the original untreated egg ; 

 when inside, the bottle may be filled with brine, or weak solution 

 of ammonia, when the egg will gradually return to its original 

 shape, and become somewhat hardened so as to preserve its form 

 instead of being soft and pulpy. By placing the bottle full of 

 brine in a saucepan of cold water and very gradually heating this 

 up until it boils, removing the source of heat after boiling a few 

 minutes, and allowing to cool again slowly, it is possible to cook 

 and hard-boil the prepared egg inside the bottle without cracking 

 the glass ; so that if the bottle be then broken and the egg 

 extracted, it will be found hard and sound and fit to eat (if the 

 original egg was a fresh one). To any one unacquainted with 

 the way in which the matter is managed it seems an impossibility 

 to get a genuine hard-boiled egg inside a narrow-necked bottle. 



Expt. 253. To make Bones pliable. The bones of animals 

 differ from the outside skeletons or shells of molluscs and crustaceans 

 (snails and oysters, lobsters, and such like creatures) in that the latter 

 consist of animal tissue strengthened up and hardened by mineral 



