52 § 46. BASES A^STD ACIDS AVITH REAGENTS. 



and the loop is then held at the end of the inner blow- 

 pipe flame, or in the corresponding part of the flame of a 

 Bunsen's gas-burner, a yellow color is commuiiicated to 

 the flame beyond the wire. 



These yellow rays are completely absorbed by blue 

 glass of suflicient thickness. This test for sodium is very 

 delicate, and is not masked by even a considerable pro- 

 portion of any other metal, except copper and calcium. 

 The presence of a very large proportion of potassium 

 may conceal the sodium reaction. In that case, green glass 

 will absorb the violet rays of the potassium flame, but 

 will not aflfect the colored rays produced by the sodium. 



Quantitative estimation. — a. Sodium, like potassium, 

 may be weighed as chloride or as sulphate, on evaporat- 

 ing the solution to dryness, from which all other acids 

 except hydrochloric or sulphuric have been removed by 

 the methods described in each special case. 



The operations of evaporation and ignition may be 

 conducted precisely as directed for the treatment of the 

 corresponding potassium compounds (§ 44), except that 

 no provision need be made to guard against loss by the 

 decrepitation of the sodic sulphate. 



Sodic sulphate, Na^SO^, contains 32.39° [^ of sodium or 

 43.66"! „ of soda, Na^O. Sodic chloride contains 39.32" |„ 

 of sodium. 



h. If potassium is present, the two metals being con- 

 verted into chlorides, ascertain the amount of the same 

 by evaporation to dryness and weighing the residue after 

 gentle ignition, as directed for the treatment of potassic 

 chloride (§ 44, «), and then determine the amount of po- 

 tassic chloride in this mixture, with the aid of platinic 

 chloride, as directed under potassium (§ 44, c). The dif- 

 ference between the sum of the two chlorides and the 

 amount of potassic chloride will give the sodic chloride. 



In this separation, enough platinic chloride must be 



