202 GEOLOGY AND CHEMISTRY OF SOILS. 



plete, weigh again, and the loss of weight is the amount of or- 

 ganic matter in the soil. Note it in the laboratory journal, B. 



3. To determine the amount and nature of matters soluble 

 in muriatic acid, which will take up all the mineral substances 

 that can be acted upon by vegetation, such as all salts of lime, 

 iron, alumina, manganese, magnesia, potash, etc., place the 

 burned soil B in a clean green glass flask, with a thin bottom, 

 pour over it a small quantity of distilled water, sufticient to 

 cover it, then drop in some muriatic acid, and note whether 

 there is any effervescence. If so, there is a carbonate, proba- 

 bly of lime, in the soil. Add more acid, say about one ounce, 

 diluted with an equal bulk of water. Boil tlie whole, for half 

 an hour, or until the residuary matter is nearly white. Every 

 thing soluble in the acid is then taken up. Dilute with 

 distilled water and throw the whole upon a double filter. Af- 

 ter the hquid has passed through the paper wash the insoluble 

 matter on the filter by means of a stream of boiling hot water, 

 and continue the operation until the water comes through taste- 

 less. Dry the filters with their contents, separate them and 

 bm-n them separately, weighing one against the other. The 

 difference is the weight of the insoluble silicates, and is gener- 

 ally nearly pure si lex. Note its weight, C. 



4. In order to ascertain the nature and proportions of the 

 matters that have been dissolved by the muriatic acid, you may 

 proceed as follows : 



Take the filtered solution, which must be in a green glass 

 flask ; add to it a few drops of nitric acid, to per-oxidize the 

 iron, and boil it. Then, while still warm, add liquid ammonia, 

 until all the per-oxide of iron and alumina are precipitated. Sim- 

 mer the whole a few minutes so as to condense the bulky pre- 

 cipitate. Filter on double paper, wash the precipitate twelve 

 hours with hot water, or until the liquid passes tasteless ; then 

 separate the })recipitate while moist from the filter by means of 

 a silver knife, scraping up every portion that can be removed 

 from the filter. Place this in a large silver crucible and pour 

 over it a solution of pure potash, in distilled water. Boil until 

 the alumina is entirely taken up, and the oxide of iron left has 

 a deep brown color. You may know that a sufticiency of pot- 

 ash has been added by letting fall into the solution a drop of 

 muriatic acid, when flocculi of alumina will preci[)itatp, but will 

 immediately redissolve if there is potash enough. Dilute with 

 distilled water, filtrate through double filters, wash the precipi- 

 tate, dry the filters and their contents, sej)arate them, and burn 



