106 SCIENTIFIC AMUSEMENTS. 



liquid will get hot, and if not well cooled by immersing the body 

 of the flask in a bucket of water, or holding it under a tap of 

 running water, it will give off steam; gradually add the rest of 

 the acid with continual cooling; finally, when the two liquids 

 have been completely intermixed, and the mixture has cooled 

 down completely, pour the mixture back into the two original 

 measuring vessels. It will be found that, even when the greatest 

 care is taken to avoid any loss by spilling or evolution of steam, 

 there will be a considerable deficiency in volume, far greater than 

 would be accounted for by the few drops of liquid remaining in 

 the. flask ; thus showing that a considerable contraction has taken 

 place. 



A similar diminution in bulk is noticeable when water and 

 alcohol and many other liquids are mixed together; also when 

 metals are intermixed by melting to form certain alloys, the 

 volume of mixture being less than that of the different metals 

 used to make it. 



Caution. Whenever you are making experiments requiring the 

 use of oil of vitriol, be very careful how you add water or watery 

 fluids to it, or how you pour it into water, as much heat is evolved 

 during the mixture, which under certain circumstances may evolve 

 sufficient steam to scatter the acid about, and do serious damage 

 to the skin, eyesight, clothing, or surrounding objects. Never 

 pour icater into hot sulphuric acid; and if you want to prepare 

 diluted acid by mixing oil of vitriol with water, do not make it in 

 a thick glass vessel (such as a tumbler), as the heat is very liable 

 to crack the glass; a stoneware jug is much safer, pouring the 

 acid into the water little by little, and stirring up the while with 

 a bit of glass rod. 



CHAPTER IX. 



SPONTANEOUS INTERMIXTURE OF GASES WITHOUT CHEMICAL 

 ACTION TAKING PLACE : GASEOUS DIFFUSION. 



When two gases not capable of acting chemically upon one 

 another are brought into contact in such a fashion that no 

 mechanical intermixture takes place spontaneously on account of 

 one being lighter than the other and so rising, or by stirring, &c., 

 and none by the setting up of convective currents due to difference 



