35 



the whole sample of the soil to a state of uniform mixture, and to re- 

 move from it the coarser gravel and roots, &c., which it may contain. 



DETERMINATION OF MOISTURE AND OF VOLATILE AND ORGANIC 



MATTER. 



Moisture. Introduce from 2 to 5 grams of the air dried soil into a pre. 

 viously weighed platinum dish holding about 10 c. c. and dry at 120 

 C. in an air-bath for eight hours, cool in a desiccator, and weigh, Re- 

 peat the heating and weighing until the substance ceases to lose weight 

 or begins to increase, indicating incipient oxidation. From the lowest 

 weight thus obtained calculate the percentage of moisture. The differ- 

 ence between the first weight of the platinum dish and substance and 

 that found on drying represents the moisture, and this weight divided by 

 the quantity taken and the quotient obtained multiplied by 100 will give 

 the percentage. The results are only approximate, as the complete dry- 

 ing of a soil, especially if it contains much clay or organic matter, is very 

 difficult to effect. Some soils are very hygroscopic and rapidly absorb 

 the atmospheric moisture; for this reason the platinum dish should be 

 cooled in a desiccator containing fused calcium chloride and rapidly 

 weighed. 



Volatile and organic inatter. The dried substance is then ignited. at 

 a low red heat, in a muffle furnace, until the whole of the organic mat- 

 ter has been destroyed, care being taken that the heat is not raised 

 too high in order to avoid driving off any of the alkaline chlorides, &c. 



The residue is ordinarily of a reddish color, owing to the sesquioxide 

 of iron which it contains. When the mass is cool it is treated with a 

 few drops, about 1 c. c., of a saturated solution of ammonium carbonate 

 or oxalate, and then gradually heated to about 150 C. in the air-bath, 

 avoiding all danger of loss by sputtering by a careful regulation of the 

 heat at the commencement. By this means any carbonates that may 

 have been decomposed by the ignition are reconverted. 



The loss in weight represents the organic and other volatile matters. 



TREATMENT OF THE SOIL WITH HYDROCHLORIC ACID (Sp. gT. 1.115). 



In using the different reagents and distilled water especial care must 

 be taken that they are all chemically pure, in order that no foreign mat- 

 ter may be introduced into the analysis by them ; for this purpose they 

 must be carefully tested. It is hardly necessary to add that all the 

 weighing of precipitates, &c., must be done on a delicate analytical 

 balance. 



The hydrochloric acid used is made from the concentrated acid, C. P., 

 by diluting with distilled water until it attains a specific gravity of 

 3 .115 as shown by an hydrometer, or, better, taken in a specific gravity 

 bottle, and its weight compared with that of an equal volume of water 

 at the same temperature. 



