§ 122. CHILI SALTPETRE. 239 



E and G). The determination of potassa in common 

 salt is generally unnecessary. 



B. Potassa salts. — Dissolve 10 grms. in hot water, and 

 determine potassa at once with platinic chloride in a por- 

 tion of the solution (§ 93, G, 3). 



For the complete analysis, or the determination of 

 water, proceed as directed for the analysis of salt. 



CHILI SALTPETRE. 



122. a. Water.— Desiccate 3 grms. at 110° C. 



h. Complete analysis. — Treat 20 grms. of the pulver- 

 ized salt w4th hot water, filter the solution into a litre 

 flask, collect the insoluble residue on a dried and weighed 

 filter, wash it well with hot water, dry it at 125° C, 

 weigh it, and then ignite it at a low temperature, and 

 weigh the ash. These results give the amount of insolu- 

 ble sand and day^ and, approximately, the organic matter. 



Bring the volume of the aqueous solution to 1000 c.c, 

 determine sulphuric acid and chlorine in two portions of 

 200 c.c. each, by precipitation with baric chloride (§ 59) 

 and argentic nitrate (§ 63), and lime and magnesia in an- 

 other portion of 500 c.c. (§ 50, IS). 



c. Soda. — This may be estimated by the difierence 

 between the total amount of substance taken, and the 

 sum of the acids, water, organic matter, and the other 

 bases ; or it may be estimated by converting all the bases 

 into sulphates, in the manner described for converting 

 potassa into sulphate (§ 44), and weighing the mixture 

 of the salts ; then subtract from this the sum of the 

 weights of calcic and magnesic sulphate, as estimated from 

 the determination of those bases, already made, and the 

 remainder will be the sodic (and potassic) sulphate. 



d. To determine approxim.ately the amount of potassa^ 

 if any is present, dissolve this residue of mixed sulphates 



