of water, and, when completely cool, adding this to a litre of nitric acid 

 of specific gravity 1*20 axe added, and the mixture is heated to a 

 temperature of 50C for three hours in a water oven, and allowed to cool 

 completely. The liquid is decanted through a small filter, and the pre- 

 cipitate remaining in the flask repeatedly washed with diluted (1:1) 

 molybdic solution. It is then dissolved, oil the filter, with warm 5 per 

 cent, ammonia, and to the resulting solution, while still warm, hydroch- 

 loric acid is added at once, but gradually, until the precipitate at first 

 formed dissolves only after long agitation. After cooling 20 c.c. of Mag- 

 nesia mixture* are added from a burette, drop by drop, at the rate of one 

 drop every five seconds, and then 25 c.c. of 5 per cent, ammonia. The 

 mixture is allowed to stand for twelve hours at least, after which the pre- 

 cipitate is collected in a weighed Gooch crucible, and washed with 5 per 

 cent, ammonia. It is then dried on a heated iron plate, and ignited in 

 a furnace for fifteen minutes. The crucible is then cooled and weighed 

 -with the magnesium pyrophosphate. 



METHOD II. HYDROCHLORIC ACID EXTRACTION AS PRACTISED BY THE 

 GERMAN EXPERIMENT STATIONS.! 



To 200 grammes of dry-sifted " true soil " are added 400 c.c. of a 

 25 per cent, hydrochloric acid solution, the quantity of acid being in- 

 creased, if necessary, when the soil contains an excess of carbonates. The 

 mixture is allowed to stand a,t the ordinary temperature for 48 hours, 

 with frequent shaking, and is then filtered. 



Determinations of lime and potash are made in definite quantities of 

 the filtered extract (prepared as in Method I), exactly as in the first 

 method. 



Determination of Phosphoric oxide. 20 c.c. of the filtered extract 

 (which has been treated in a similar manner to the extract in. Method I), 

 equivalent to 10 grammes of " true soil," are placed in a dish and evapor- 

 ated almost to dryness. The residue is taken up with a little nitric acid, 

 washed into a suitable Erlenmeyer flask, and nearly neutralised by means 

 of strong ammonia solution, a few drops of nitric acid being used to 

 acidify the mixture should the neutral point be passed. Molybdic solu- 

 tion is then added, and the rest of the process conducted aa in the first 

 method. 



METHOD III. EXTRACTION OP IGNITED SOIL BY MEANS OF HYDROCHLORIC 



ACID, AIDED BY NlTRIC ACID. (MAERCKER's METHOD.) 



Twenty grammes of "fine earth" are weighed in a platinum dish, 

 and heated on asbestos wire gauze until all organic matter has been ex- 

 pelled. The dish is then cooled and the contents carefully transferred 

 by the aid of a brush into a porcelain dish. 100 c.c. of concentrated 

 hydrochloric acid and 10 -c.c. of concentrated nitric acid are now added, 

 and the mixture is evaporated on a water bath, and dried for three hours 

 at 120 C. Warm water is next added, together with some dilute hydroch- 

 loric acid, and the whole is washed into a marked 500 c.c. flask, in which 

 it is boiled for 15 minutes. The mixture is then cooled, filled up to the 

 mark with distilled water, and filtered. 



Determination of Lime. 100 c.c. of the filtered extract (equivalent 

 -to four grammes of fine earth) axe placed in a 200 c.c flask, two or three 

 drops of rosolic acid are added, and the determination is proceeded with 

 similarly to that in Method I. 



* This Magnesia mixture is prepared by dissolving 110 grammes of magnesium 

 chloride, and 210 grammes of ammonium chloride, in 700 c.c. of 24% ammonia solution 

 filtering the mixture, if turbid, and diluting with distilled water to two litres. 



t Land. Versuchsstat, Vol. 38, p. 311. 



