Potash and Soda. 57 



of the weight of this double salt. The weight of the potash 

 being known, and likewise the weight of the two chlorides 

 of potassium and sodium, it is easy to deduce that of the 

 soda. 



I consider the following method easier than this, espe- 

 cially when the quantity of potash and soda to be separated 

 is considerable, and I have found that young analysts learn 

 very soon to employ it with accuracy. 



1 . Convert the mixture of potash and soda into sulphates, 

 render these sulphates anhydrous by ignition in a platinum 

 crucible, and determine their weight. Let it amount to 

 29 grains. 



2. Dissolve the two sulphates in water, and throw down 

 the sulphuric acid by chloride of barium. Wash the sul- 

 phate of barytes obtained, dry it and weigh it after ignition. 

 Let the weight be 43"5 grains, indicating 15 grains of sul- 

 phuric acid. 



3. Separate any excess of barytes that may have been 

 added to the liquid by the cautious addition of dilute sul- 

 phuric acid. Filter, evaporate to dryness and ignite. The 

 salt thus obtained will consist of the mixture of potash and 

 soda converted into chloride of potassium and sodium. 

 Weigh this salt. Let the weight be 24-5 grains. 



Now, the atom of potash is 6, and that of soda 4 : and 

 it is obvious from paragraphs 1 and 2 that the mixture of 

 potash and soda weighs 14. 



Let the atoms of potash in the mixture be x, and those of 

 soda y, it is plain that we have 



6 x + 4 y = 14 and x = J 



By comparing paragraphs 3 and 4, it is obvious, that the 

 weight of chlorine in the 24 - 5 grains of the mixed chloride 

 obtained is 13*5 grains. For it must be equivalent to the 

 15 grains of sulphuric acid. In this mixed chloride the 

 potash is converted into potassium, and consequently its 

 atom weighs only 5, while the atom of sodium weighs 3. 

 We have, therefore 



bx + 3w + 13-5 = 24-5 and x = ll ~ 3 'i 



5 



If we equate these two values of a; we have 



14 — 4y = II — 3 y 



b 5 



