36 or THE SOLUBLE .^J^L'.NK xMATTEU IN THE SOIL. lAppCud^X^ 



saline matter under examination. If any sulphuric acid be present in it add ni- 

 trate of baryta drop by drop to the solution till the whole of the acid is exactly 

 thrown down — if possible, no excess of baryia being left in the solution — then 

 precipitate the alumina and oxides of iron and manganese, and the lime, if any 

 of these be present, and, finally evaporate to dryness, and heat to redness as be- 

 fore. The dry mass is now to be dissolved in water, adding, -if necessary to 

 complete the soliUion, a few drops of jiiuriD.ic acid. A quantity of red oxide of 

 mercury is then to be added to the concentrated solution, and the whole boiled 

 down to dryness. AVater now dissolves out the potash and soda only, and 

 leaves the magnesia mixed with oxide of mercury. I'his is to be collected on 

 a filter, washed — not with too much water — and heated to redness, when the 

 magnesia remains pure, and may be weighed. 



g. Es-iniaiion of the Pot;tsk ani S'xta. — The solution containing the potash 

 and soda, is to be evaporated to dryness, and heated to redness to drive off any 

 mercury it may contain. The weight of the mass which consists of a mixture 

 of chloride of potassium with chloride of sodium (coinmon salt) is accurately 

 determined, it is then dissolved in a small quantity of water, and a solution of 

 bi-chloride of platinum added to it in sufficient quantity. Being evaporated by 

 a very g ntle heat nearly to dryness, weak alcohol is added, which dissolves the 

 chloride of sodium and any excess of salt of platinum which may be present. 

 The yellow powder is collected on a weighed filter, washed well with spirits, 

 dried by a gentle heat and weighed on the filter. Every 100 grains indicate 

 the presence of 19'33 grains of potash, or 3056 grains of chloride of potassium. 

 The quantity of chloride of sodium is estimated from the loss. The weight 

 of the chloride of potassium above found, is deducted from that of the mixed 

 chlorides previously ascertained, the remainder is the weight of the chloride of 

 sodium. Every 100 grains of chloride of sodium (common salt) are equiva- 

 lent to 53-29 of soda. 



k. EsUmation of the Amnioiria. — If ammonia be present in the solution along 

 with potash and other substances, the method by which it can be moist easily 

 estimated is to introduce the solution into a large tubulated retort, to add water 

 until the solution amounts to nearly an English pint — then to introduce a quan- 

 tity of caustic potash or caustic baryta, and to distil by a gentle heat into a 

 close receiver, containing a little dilute muriatic acid, until fully one half has 

 passed over, Bi-chloride of platinum is then to be added to the solution, 

 which has come over, previously rendered slightly acid by muriatic acid, and 

 the whole is evaporated nearly to'dryness by a very gentle heat. Dilute alco- 

 hol is then added to wash out the excess of the salt of platinum, and the yellow 

 powder is collected on a filter, washed with spirit, dried by a very gentle heat, 

 and weighed. One hundred grains indicate the presence of 7-69 grains of 

 ammonia. 



Or the yellow powder, without being so carefully dried, may be heated to red- 

 ness, when only metallic platinum will remain. One hundred grains of this 

 metallic platinum indicate the presence of 17 39 grains of ammonia. 



i. Estimation of the Phosplioric Acid. — If phosphoric acid be present in the 

 solution, it will be contained in the precipitate thrown down by ammonia {d). 

 As it will never be found but in very small quantity, the rigorous determination 

 of its amount is a matter of considerable difliculty. The following method 

 already described (13°, //,) may be adopted. The precipitated alumina, oxide 

 of iron, &c., thrown down by ammonia, after being dried, are to be mixed with 

 three times their weight of pure dry carbonate of soda, and fused together in a 

 platinxim crucible. The fused mass is then to be treated with cold distilled 

 water till every thing soluble is taken up. The filtered solution- is next te be 

 gently heated and exactly neutralized with nitric acid, when a solution of ni- 

 trate of silver Avill throw down a ivhite precipitate of phosphate of silver, which 

 is to be collected, dried, and weighed. Every hundred grains of it are equal to 

 23-51 of phosphoric acid, c ' 48*50 of bor.3 earth. 



