§ 46. SODIUM. 51 



make it of the normal strength. When the solution has 

 been prepared according to these directions, and the water 

 and alkali are well mixed, it should be tested, to be sure 

 that the equality between the acid and the alkaline solution 

 is perfect. Keep the solution in a bottle closed with a 

 cork, through which passes a calcic-chloride tube that is 

 stopped at its lower end with a plug of cotton and then 

 filled with soda-lime ; by this arrangement; the free ex- 

 pansion of the air in the upper part of the bottle with 

 changes of temperature is permitted, while no carbonic 

 acid can enter ; it is well to bend the slender part of the 

 calcic-chloride tube at a right angle just above the cork, 

 so that no soda-lime can possibly fall into the bottle, and 

 to fill the burette by means of a small siphon passing 

 through the cork to the bottom of the boUle, the longer 

 arm of which may be closed at the end by a clamp on a 

 rubber tube. 



To 100 c.c. of this solution add 900 c.c. of water, mak- 

 ing both measurements with the utmost care, mix well, 

 and test this solution with the standard acid ; 1 c.c. of 

 the latter should require exactly 10 c.c. of the former to 

 neutralize it ; keep this solution in the same manner as de- 

 scribed for the other standard soda solution, and labeled, 

 ^ Ijo standard soda solution. 



SODIUM. Na. 23. 



46. Salts of sodium, with all the acids named in § 43, 

 are soluble in water. The double chloride of sodium and 

 platinum is also soluble in both water and alcohol. 



When this solution is very slowly evaporated to dry- 

 ness, slender, rosy, prismatic crystals are formed, while 

 the crystals of the corresponding potassium salt are octa- 

 hedral and granular. 



Reactions. — ^When a drop of a solution of a salt of so- 

 dium is evaporated to dryness in the platinum-wire loop, 



