US THE ESTIMATION OP POTASH AND PHOSPHORIC ACID. 25 



as the precise arrangement will not affect the value of the sample, nor cause 

 any alteration in the sum of the constituents, while there appears to be no 

 reliable evidence of the actual mode of combination. 



In the case of " muriates," aud sulphates having an alkaline reaction, such 

 as those made from kelp and beetroot, potassium and sodium arc the only two 

 metals present in larger quantities than traces. In the statement of all 

 such analyses your Committee is of opinion that the only proper method is 

 to calculate the potassium as sulphate, chloride, and carbonate in succession, 

 assuming no sodium to exist as sulphate or chloride unless the amount of 

 potassium present is insufficient to satisfy the latter or both of those salt 

 radicals. 



The impossibility of the coexistence of sodium sulphate or chloride with 

 potassium carbonate is proved by the fact that double decomposition occurs 

 when solutions of these salts are mixed and concentrated. 



The non-deliquescent character of kelp sulphates and muriates also furnishes 

 a strong independent proof of absence of potassium carbonate. 



The same principles apply to the statement of the results of the analyses 

 of commercial carbonates of potassium, and in their case its adoption becomes 

 still more important. 



In the case of saltpetres only that portion of the potassium can be pro- 

 perly considered to exist as nitrate which is in excess of the quantity 

 required for calculation as potassium sulphate (after allowing for the sul- 

 phate present as calcium sulphate) ; whether some of the potassium will also 

 exist as chloride, or whether there will be some sodium nitrate present, must 

 depend on the respective amounts of potassium and N0 3 found ; but having 

 regard to the well-known reaction KCl+NaN0 8 =NaCl+KNO s3 your Com- 

 mittee is of opinion that the presence of both chloride of potassium and 

 nitrate of sodium in the same sample is improbable. 



In brief, the Committee is of opinion that in calculating the results of 

 analyses of potash salts, the following method should be adhered to in com- 

 bining the various metals and salt radicals present in the portion of the 

 sample soluble in water. 



Basic hydrogen, which is met with only in artificial sulphates, exists as 

 sulphuric acid, or, more strictly spcakiug, as potassium-hydrogen-sulphate, 



KHS0 4 . . 



Calcium docs not occur in practice in excess of an equivalent amount ot 

 sulphate, so that it should always be calculated to CaS0 4 . 



The remaining constituents of the soluble portion of the sanrple should bo 

 arranged on the principle of combining the strongest metal with the strongest 

 salt radicals. 



The order of affinity which the Committee considers most in accordance 

 with observed facts and theoretical propriety is shown in the following list, 

 in which tho strongest metals and salt radicals are placed first : — 



Potassium. Sulphate. 



Sodium. Nitrate. 



Magnesium. Chloride. 



Iron. Carbonate. 



Tho Committee is of opinion that in all cases in which one of the con- 

 stituents of a sample is determined by subtracting the sum of the others 

 from 100-00, the fact ought to be indicated in the statement of results. 

 This can readily be done by appending the words " by difference '' or " esti- 

 mated by difference " to the name of the constituent thus determined. The 

 adoption of this plan would obviate many of the disadvantages attendant on 



