No. v.} OP THE SOLUBIiE SALINE MATTER IN THE SOIL. 37 



Or the filtered solution may be treated with muriatic acid, ammonia added in 

 excess, and then a solution of chloi'ide of calcium. Bo7i/; earlli will fall, which 

 is to be collected, washed, heated to redness, and weighed. One hundred 

 grains of it contain 4845 of piiosphoric acid. Tlie former method is probably 

 tiie better, but neither of them will give more than an approximation to the truth. 



I'hat portion of the fused mass wliich cold water has refused to take up is to 

 be dissolved in mui-iatic acid, and again precipitated by ammonia. The clear 

 solution which passes through is to be added to the first ammoniacal solu- 

 tion (r), from which the lime is not yet thrown down, as when little alumina 

 and oxide of iron are present, a small portion of lime and magnesia, if con- 

 tained in the salt under examination, may have fallen along with them in com- 

 bination with phosphoric acid. 



The alumina and oxide of iron which rest on the filter are to be separated 

 and estimated as already described (./). 



k. Esthnaiion of Ike Curijo7uc Add. — The lime and magnesia dissolved by 

 cold diluted muriatic acid are partly in combination with cai-bonic acid and 

 partly with the humic, ulmic, and other j^egetable acids. To determine the 

 carbonic acid, 100 grains of the soil dned at "il^^, are to be introduced into a 

 small weighed flask, and then just covered by a weighed quantity of cold di- 

 luted muriatic acid. After 12 hours, when the action has ceased, a small tube 

 is to be introduced into the flask and air sucked through it till the whole of the 

 carbonic acid is drawn out of the flask. The loss of weight will indicate the 

 amount of carbonic acid very nearly. It would be more rigorously ascertained 

 by fitting into the mouth of the flask a tul^e containing chloride of calcium, 

 and then heating the solution to expel the carbonic acid. 



Kvery hundred grains of carbonic acid indicate the presence of 77-24 grains 

 of lime in the state of carbonate. The weight of lime in this state, deducted 

 from the whole weight obtained as above (c), gives the quantity which is ii 

 combination with othev organic acids. 



IV. or THE INSOLUBLE EARTHY MATTER OF THE SOIL. ^ 



15^'. When the soil has been washed with distilled water as above directed — 

 it is to be treated in the cold with diluted muriatic acid — and allowed to stand 

 with occasional stirring for 1-2 hours. By this means the carbonates of lime, 

 magnesia, and iron, and the phosphates of lime, and alumina, are dissolved — 

 with any lime, magnesia, oxide of iron, or alumina, which may have been in 

 combination with organic acids. The iron, alumina, and phosphoric acid are 

 to be precipitated by ammonia, the lime by oxalate of ammonia, and such other- 

 steps taken as may be necessary, according to the methods already described. 



lo^^. The undissolved portion may now be treated with hot concentrated 

 muriatic, kept warm and occasionally stirred for two or three hours, and the 

 solution afterwards evaporated to dryness. The dry matter is then to be 

 moistened with a few drops of muriatic acid, and subsequently treated with 

 water. What remains undissolved is silica, which must be collected on a 

 filter, dried, heated to redness, and weighed. 



The solution may contain oxide of iron, alumina, lime, magnesia, potash, 

 and soda. Any of the four last substances, which may be detected in it, have 

 most probably existed in the soil, in combination with silica — in the state of 

 silicates. 



17°. But the soil may still contain alumina, not soluble in hot muriatic acid. 

 To ascertain if this be the case, and to separate and determine this portion of 

 the alumina, if present, either of two methods may be adopted. 



a. The residual soil may be drenched with concentrated sulphuric acid and 

 heated for a considerable time till the sulphuric acid is nearly all driven off. 

 On treating with water, and adding ammonia to the filtered solution, alumina, 

 and oxide of iron, if any have been present, will be thrown down. If any 

 alumina be thus separated, tks treatment with sulphuric acid must be repeat- 



