1846.] Analysis of Soils. 229 



oxalate of ammonia to throw down any lime that may be present. 

 The solution is now free from any fixed bases except the alkalies, 

 and may be evaporated to dryness in a porcelain capsule and re- 

 dissolved in water, filtered, and evaporated, and heated to redness 

 in a platina capsule to expel all the ammoniacal salts. There 

 remains in the capsule a white mass of saline matter which con- 

 sists of the sulphates of the alkalies. Their weight is to be as- 

 certained by counterpoising the capsule in the balance and then 

 dissolving out the alkaline salts, the clean and dry capsules being 

 restored to balance, and again brought to equipoise; by adding 

 weights to the capsule we learn the weight of the saline matters 

 that had been removed. 



The saline solution is next to be decomposed by means of 

 chloride of barium dissolved in water. The barytic solution be- 

 ing added a little at a time, until there is no longer any precipi- 

 tate of sulphate of baryta. The solution is then to be filtered, 

 and may be again evaporated to dryness, and the weight of the 

 mixed chlorides of potassium and sodium may be determined. 

 Then redissolve in a little water and add a solution of chloro- 

 platinic acid in excess, and evaporate again to entire dryness, 

 but at a temperature not much above that of boiling water. 

 Pour pure alcohol into the capsule, and dissolve out the chloro- 

 platinate of soda, and the chloroplatinate of potash will remain 

 undissolved. It is to be collected on double filters, dried, and one 

 filter is to be weighed against the other; the ditference of weight 

 is that of the chloroplatinate of potash, from w^iich the weight of 

 the potash is calculated. The weight of the potash being known 

 it is easy to deduce that of the soda by difference, or we may de- 

 com}X)se the chloroplatinate of soda, by sulphydric acid gas, and 

 filter and evaporate to dryness. Convert the soda into a sulphate 

 by sulphuric acid, drive off the excess of sulphuric acid by heat, 

 and weigh the sulphate of soda, from which we calculate the 

 proportion of pure soda. 



If any magnesia was present in the silicate analyzed, another 

 series of operations are required for its separation from the alka- 

 lies. We convert the sulphates into chlorides, as above described, 



