CHEMICAL ANALYSIS OF SOILS. 203 



and weigh them against each other. The difference of their 

 weight is that of the per-oxide of iron. Mark its weight 

 against D. 



5. To separate the alumina, you must now take its alkaline 

 solution and acidulate it with muriatic acid ; then add a solu- 

 tion of carbonate of ammonia in pure water. All the alumina 

 will be thrown down in the state of a white, gelatinous, and 

 flocky precipitate. Collect it on a double filter, wash it for 24 

 hours with boiling distilled water, dry it, separate and burn the 

 filters. Weigh one against the other, and the diflference of 

 their weight will be the weight of the alumina. Mark this 

 against E. 



Now you may go back to the ammoniacal solution, from which 

 the iron and alumina have been separated, but in practice the 

 following processes are carried on while we are waiting for the 

 filtralions and washings of the alumina and oxide of iron. 



This ammoniacal solution may contain the lime, magnesia, 

 and a small quantity of manganese. Add to it a solution of ox- 

 alate of ammonia which will precipitate all the lime in the 

 state of an oxalate. Let this precipitate subside, and then col- 

 lect it on double filters, washing it with warm water. Dry the 

 filters with their contents, separate them and burn one against 

 the other at a red heat in a platina capsule ; let fall a few drops 

 of a solution of carbonate of ammonia upon the lime, heat it 

 again to dull redness. Weigh the result against its counter- 

 poised burnt filter, and you will have the quantity of lime in 

 the state of a carbonate, and may reduce it by calcidation to 

 any other salt of lime that you have found to exist in the soih 

 Mark the weight of this against F. 



6. To separate the magnesia, add to the solution from which 

 the lime has been separated, a solution of phosphate of soda, 

 (it being still ammoniacal,) when the magnesia will be thrown 

 down in the state of an ammoniaco-iiiagnesian phosphate. Col- 

 lect it on a filter, wash it but little, then dry the filters and con- 

 tents, separate them, burn one against the other in a platina 

 capsule. The difference of weight will be the weight of the 

 bi-phosphate of magnesia, 40 per cent, of which may be re- 

 garded as equivalent to the magnesia contained. G. 



7. You may now run a current of sulphureted hydrogen gas 

 through the remaining solution, or add bi-hydro sulphate of am- 

 monia, when all the manganese will be thrown down in the 

 state of a sulphuret. Collect and reduce it to black oxide. H. 



The analysis is complete so far as it can be done on this spe- 



