1846.] Analysis of Soils. 227 



alkali, and the per-oxide of iron remains of a brown color. We 

 ascertain when a sufficient quantity of potash has been added to 

 dissolve all the alumina, by letting fall a drop of chlorohydiic 

 acid into the solution, when a little of the alumina will be thrown 

 down, and if there is an excess of potash it will soon redissolve. 

 Collect the per-oxide of iron on double filters, and wash so long as 

 traces of alkali remain. Then dry and burn the filters separately, 

 and weigh as before described. Let us suppose the per-oxide of 

 iron weighs 2 grains. 



We next have to separate the alumina from its potassic solu- 

 tion. This is done by rendering the sqlution acid by means of 

 an excess of chlorohydric acid, and then by adding a solution of 

 carbonate of ammonia in excess, which throws down all the alu- 

 mina in the state of a white jelly. Collect it on double filters, 

 wash with boiling water so long as any spot remains on evapo- 

 rating a drop of the filtered solution to dryness on a piece of pla- 

 tina foil; dry and ignite, and weigh the filters separately, and 

 note the weight of the alumina. Let us suppose it to be 3 grains. 



We next return to the ammoniacal solution from which the 

 alumina and per-oxide of iron had been separated, and analyze 

 that. We add to it an excess of oxalate of ammonia, which pre- 

 cipitates all the lime as an oxalate; filter wash and ignite, and 

 weigh the carbonate of lime produced by burning the oxalate, 

 and from the weight of the carbonate we calculate the quantity 

 of lime that existed in the silicate. Let us suppose that the car- 

 bonate of lime obtained weighed 1 grain, then since carbonate of 

 lime contains 56.29 per cent of lime, we shall have 0.56 lime 

 that was combined with silicic acid in the insoluble silicate. 



After separation of the lime from the solution we throw down 

 the magnesia by means of phosphate of soda, ammonia being 

 present in excess. Phosphate of magnesia and ammonia is pre- 

 cipitated, and after remaining in a warm situation for twelve 

 hours, the solution may be filtered, and the phosphate collected. 

 Wash, dry, ignite, and weigh the bi-phosphate of magnesia pro- 

 duced, and 40 per cent of it will be magnesia. If we obtained 

 0.6 bi-phosphate of magnesia, 0.24 would be the proportion of 



