756 SUBANTARCTIC ISLANDS OF NEW ZEALAND. [Soils and Soil-formers. 



METHODS OF ANALYSIS. 

 Analysis of Peat Soils. 



Loss on Air Drying. — The soil was exposed to the air in thin layers on shallow 

 trays, and as the soil dried it was broken by hand. When fine enough it was put 

 through a 2 mm. sieve, and then kept on the tray until it ceased to lose weight — 

 an operation extending over several days. 



Moisture. — The soil was heated to 100° C. in a platinum dish until it was of 

 constant weight. 



Hydrocarbons. — A weighed quantity of soil was placed in a platinum crucible, 

 well covered, and heated to low redness until the production of volatile inflammable 

 vapours ceased. 



Fixed Carbon. — The residue from estimation of hydrocarbons was heated to 

 dull redness, with the cover of the crucible removed, until the carbon was entirely 

 consumed. 



Water-soluble Salts. — To each 10 grams of soil 100 c.c. of water were added, 

 placed in mechanical shaker and shaken for five hours, and filtered. In an aliquot 

 part of the filtrate the chlorine was estimated as silver-chloride. 



Total Soluble Salts. — An aliquot part was exaporated to dryness in a platinum 

 dish heated at 100° C. till constant weight, and weighed. 



Soluble Organic Matter. — The dried residue from total soluble salts was ignited 

 at low temperature, the loss being calculated as organic matter. The residue from 

 the ignited salts was analysed for sulphuric acid, silica, iron and alumina, lime, 

 magnesia, phosphoric acid, and alkalis. 



Citric-acid-soluble Salts. — These were extracted by Dyer's method. Hall's 

 modification (J. Chem. Soc. Trans., vol. Ixxxix, pt. 2, 1906).* 



Hydrochloric-acid- soluble Salts. — Twenty grams of the dried soil was ignited, 

 taken up with hydrochloric acid, evaporated to dryness, repeated, filtered, and 

 washed with dilute HCl, made up to 250 c.c, and aliquot parts taken for estimation 

 of iron and alumina, lime, magnesia, phosphoric acid, and potash. 



Total by Hydrofluoric Acid, — The ash, after estimation of hydrocarbons and 

 fixed carbons, was digested with hydrofluoric acid and sulphuric acid, and residue 

 redissolved in hydrochloric acid. Silica, iron and alumina, lime, magnesia, phos- 

 phoric acid, and alkalis estimated in aliquot parts of the solution. The " iron and 

 alumina " also contains manganese -oxide, titanium-oxide, zirconia, and possibly 

 oxides of other rare earths. 



Total Nitrogen. — Five grams of the dried soil were digested with sulphuric acid 

 and zinc dust, with the addition of mercury, until colourless. The ammonia in the 

 ammonium-sulphate formed was estimated by distillation into normal sulphuric 

 acid. 



* Wood and Berry (42) remark on the probable necessity for raising the limit below which the 

 economical use of phosphatic fertilisers is indicated, for citric-acid-soluble phosphoric acid in peaty 

 soils. This is probably due to the citric acid dissolving organic matter, including organic phosphorus 

 compounds, if the soil is rich in humus. Peat from the Isle of Ely yielding as much as 0-05 per cent. 

 P2O5 to 1 per cent, citric acid responded very profitably to phosphatic manuring. Citric acid of 

 1 per cent, strength appears not to dissolve as much organic matter from these island soils as water 

 does, 



