NOTE.--In peats containing sulphate of the protoxide of iron, the loss that occurs during ignition is partly due to the escape of sulphuric acid, which is set free by the decomposition of the above mentioned salt of iron. But the quantity is usually so small in comparison with the organic matter, that it may be disregarded. The same may be said of the combined water in the clay that is mixed with some mucks, which is only expelled at a high temperature.
IV. 3 grammes of the sample are digested for half an hour, with 200 cubic centimeters (66.6 times their weight,) of boiling water, then removed from the sand bath, and at the end of twenty-four hours, the clear liquid is decanted. This operation is twice repeated upon the residue; the three solutions are mixed, filtered, concentrated, and finally evaporated to dryness (in a tared platinum capsule,) over a water bath. The residue, which must be dried at 212 degrees, until it ceases to lose weight, gives the _total amount soluble in water_. The dried residue is then heated to low redness, and maintained at that temperature until the organic matter is burned off. The loss represents the amount of _organic matter soluble in water_, the ash gives the quantity of _soluble inorganic matter_.
V. 1 gramme is digested for two hours, at a temperature just below the boiling point, with 100 cubic centimeters of a solution containing 5 _per cent._ of crystallized carbonate of soda. It is then removed from the sand bath and allowed to settle. When the supernatant liquid has become perfectly transparent, it is carefully decanted. This operation is repeated until all the organic matter soluble in this menstruum is removed; which is accomplished as soon as the carbonate of soda solution comes off colorless. The residue, which is to be washed with boiling water until the washings no longer affect test papers, is thrown upon a tared filter, and dried at 212 degrees. It is the _total amount of organic and inorganic matter insoluble in carbonate of soda_. The loss that it suffers upon ignition, indicates the amount of _organic matter_, the ash gives the _inorganic_ matter.
NOTE.--The time required to insure perfect settling after digesting with carbonate of soda solution, varies, with different peats, from 24 hours to several days. With proper care, the results obtained are very satisfactory. Two analyses of No. 6, executed at different times, gave _total insoluble in carbonate of soda_--1st analysis 23.20 _per cent._; 2d analysis 23.45 _per cent._ These residues yielded respectively 14.30 and 14.15 _per cent._ of ash.