weighed, the difference in weight indicating organic matter, water of com- 

 bination, ammonium salts, etc. If the soil contain appreciable quantities 

 of carbonates, the contents of the crucible, before weighing, are moistened 

 with a few drops of a saturated solution of ammonium carbonate, dried, 

 and heated to dull redness, after which the crucible is placed in the desic- 

 cator to cool previous to weighing. 



Chlorine. Fifty grammes of " earth " are boiled in a marked 500 c.c. 

 flask, with about 300 c.c. of distilled water, for half an hour. Cold distilled 

 water is added until the level nearly reaches the mark, and after cooling 

 it is filled up, shaken thoroughly, and filtered, by means of a Berkefeld 

 candle filter, into a flask holding about 500 c.c., whence 50 c.c. are removed 

 for titration with T ^ Silver nitrate, using Chlorine-free Potassium chromate 

 as indicator. 



Nitrogen. Five grammes of " earth " are placed in a 150 c.c. oxidation 

 flask; a globule of mercury weighing '8 or '9 of a gramme is dropped in, 

 and a small fragment of solid paraffin to prevent frothing. 20 c.c. of con- 

 centrated sulphuric acid, free from nitrogen and nitrogen compounds, are 

 then added. The flask is closed with a loosely fitting glass stopper, and the 

 mixture heated over a Bunsen flame, gently at first, but more strongly after- 

 wards, until colourless. When cool, the stopper is removed, and the flask is 

 cautiously three-fourths filled with distilled water. It is then gently 

 shaken, and the contents are washed into a 600 c.c. Erlenmeyer flask, wash- 

 ing the oxidation flask three times, each time with about 30 c.c. of distilled 

 water : a small quantity of granulated zinc is added, and 75 c.c. of soda-lye, 

 prepared by dissolving 35 grammes of potassium sulphide in 200 c.c. of 

 water, and adding the solution to 1150 c.c. of caustic soda solution of 1*375 

 specific gravity. The distillation flask is closed with a rubber stopper 

 carrying a bulb tube which is bent above the bulb at a sharp angle and 

 terminates in a condensing tube 70 cm. long. This is connected, by means 

 of rubber tubing, with another glass tube, dipping into 20 c.c. Sulphuric 

 acid mixed with 50 c.c. jrf water in an Erlenmeyer flask as receiver. After 

 the mixture in the distillation flask has been heated to boiling, the flame 

 is so regulated that in 15 minutes' time the liquid in the receiver is at 

 boiling point. The boiling is then continued for an additional five minutes. 

 When the distillation is complete the contents of the receiver are washed 

 over into a 250 c.c. flask, filled up, and 50 c.c. are titrated with ^ Barium 

 hydrate, using Rosolic acid as indicator. 



EXTRACTION OF THE INORGANIC PLANT FOOD CONSTITUENTS FROM THE BOIL. 



The chemical analysis of a soil, if the object be to gain information 

 with respect to its agricultural qualifications, differs widely from what it 

 would be if the aim were to settle mineralogical or geological questions. 

 In the latter event the endeavour would naturally be to ascertain the 

 total quantities of mineral constituents present in the soil, quite irrespec- 

 tive of their adaptability as plant nutrients; but in the former case the 

 determination of these aggregates may be of very trifling assistance, inas- 

 much as it is highly probable that, of the total quantities of plant food 

 constituents present, only small proportions may be available to plants. 



The chemist, desiring to estimate the amount of available plant food 

 in a soil, generally tries to imitate, as closely as possible, the action of the 

 plant itself upon the soil particles. A close copy of this natural action, is 

 difficult almost to the point of impracticability, and the difficulty is not 

 rendered any the less by the fact that certain plants have a greater facility 

 of withdrawing the nutrient compounds from the soil than others have. 

 It is essential to note the distinction between " plant food constituents " 

 and " plant food." A plant food constituent remains such no matter where 

 or how it may exist; it only becomes plant food when it is present in the 

 soil, and then only when it is present there in the very condition in which 



