SODIUM. 317 



scissors to cut it like a ball of soft bread that has been kneaded in the 

 hand. It is lighter than water, and when placed in a basin of water floats 

 on the top like a piece of cork ; only it is disturbed, and takes the form of 

 a small brilliant sphere ; great effervescence is 

 also produced as it floats along, for it reduces 

 the water to a common temperature by its 

 contact. By degrees the small metallic ball 

 disappears from view, after blazing into flame 



(fig. 305). 



This remarkable experiment is very easy 

 to carry out, and sodium is now easily pro- 

 cured at any shop where chemicals are sold. 

 The combustion of sodium in water can be 



.... . ... Fig. 305. Combustion of sodium in water. 



explained in a very simple manner. Water, 



as we know, is composed of hydrogen and oxygen. Sodium, by reason of 

 its great affinity for the latter gas, combines with it, and forms a very 

 soluble oxide ; the hydrogen is released and thrown off, as we shall perceive 

 by placing a lighted match in the jar, when the combustible gas ignites. 



Oxide of sodium has a great affinity for water ; it combines with it, 

 and absorbs it in great quantities. It is a solid, white substance, which burns 

 and cauterizes the skin ; it is also alkaline, and brings back the blue colour 

 to litmus paper that has been reddened by acids. 



Sodium combines easily also with chlorine. If plunged into a jar 

 containing this gas it is transformed into a substance, which is sea salt. If 

 the chlorine is in excess a part of the gas remains free, for simple substances 

 do not mingle in undetermined ratios ; they combine, on the contrary, in 

 very definite proportions, and 35*5 gr. of dry chlorine always unites with 

 the same quantity of soda equal to 23 grams. A gram of kitchen salt is 

 formed, therefore, of 0*606 gr. of chlorine, and 0*394 gr. of sodium. Besides 

 sea salt, there are a number of different salts which may be made the object 

 of curious experiments. We know that caustic soda, or oxide of sodium, 

 is an alkaline product possessing very powerful properties ; it burns the 

 skin, and destroys organic substances. 



Sulphuric acid is endowed with no less powerful properties ; if a little 

 is dropped on the hand it produces great pain and a sense of burning ; a 

 piece of wood plunged into this acid is almost immediately carbonized. If we 

 mix forty-nine grams of sulphuric acid and thirty-one grams of caustic soda a 

 very intense reaction is produced, accompanied by a considerable elevation of 

 temperature ; after it has cooled we have a substance which can be handled 

 with impunity ; the acid and alkali have combined, and their properties 

 have been reciprocally destroyed. They have now originated a salt which 

 is sulphate of soda. This substance exercises no influence on litmus paper, 

 and resembles in no way the substances from which it originated. 



There are an infinite number of salts which result in like manner from 

 the combination of an acid with an alkali or base. Some, such as sulphate 



