NOTE IV. (p. 10).

PERCENTAGE OF FOOD VOIDED IN THE SOLID AND LIQUID EXCREMENTS.

According to Wolff, the following table shows the percentage of the dry substance of the food which is voided in the solid and liquid excrements of the cow, ox, sheep,

The excrements voided by pigs are poor in manurial constituents, because the food on which they are fed is generally of a very poor nature. In their case the urine is always very much richer in manurial ingredients than the solid excreta. The relative composition of the solid excreta and the urine will be best illustrated by quoting some experiments carried out by Wolff on this subject. The experiments were carried out with two pigs nine and a half months old, and each 121.9 kilogrammes (a kilogramme is equal to about 21 lb.) in weight. The first consumed daily 1000 grammes of barley, 5000 grammes of potatoes, and 2572 grammes of sour milk. The second one consumed the same quantities of potatoes and sour milk as the first, and 1000 grammes of peas. The following table gives the results of excreta and urine daily voided, in grammes :

NOTE VI. (p. 13).

MANURIAL CONSTITUENTS IN 1000 PARTS OF ORDINARY FOODS (Warington's' Chemistry of the Farm,' p. 139).

NOTE VII. (p. 19).

ANALYSES OF STABLE-MANURE, MADE RESPECTIVELY WITH PEAT-MOSS LITTER AND WHEAT-STRAW (by BERNARD

ANALYSES OF BRACKEN (by J. HUGHES, F.C.S.)

For a fuller discussion of this question, the reader is referred to Heiden's 'Düngerlehre,' vol. ii. p. 185, and also to Storer's 'Agricultural Chemistry,' vol. i. p. 575.

The statements in the different text-books as to the quantity of manure produced by the horse are such as naturally to perplex the student. This discrepancy is due, however, to the different methods adopted by different writers of calculating this amount. The subject is further discussed in the footnote to p. 29. The following analyses of horsemanure may be valuable for reference. They are taken from Storer's Agricultural Chemistry,' vol. i. p. 496

THE NATURE OF THE CHEMICAL REACTIONS OF AMMONIA "FIXERS."

For the student, the exact nature of the chemical reactions taking place may be of interest.

In the first place, it must be distinctly understood that the form in which ammonia escapes from the manureheap is not, as is so commonly erroneously stated in agricultural text-books, as "free" ammonia. Whenever ammonia is brought into contact with carbonic acid, carbonate of ammonia is formed. When it is remembered that carbonic acid is by far the most abundant of the gaseous products of the decomposition of organic matter, it will be at once seen that free ammonia could not exist under such circumstances.

1. In the case of hydrochloric acid, the following chemical equation will represent the nature of the reaction

2HC1 + (NH4)2CO3

(Hydrochloric

acid,)

=

2NH4Cl + H2O+CO2 (carbonate of am- (sal-ammoniac,) (carbonic acid.) monia,)

2. In the case of sulphuric acid, the equation will be

Reference has been made to the fact that magnesium sulphate may probably not only fix the ammonia, but the phosphoric acid. When magnesium sulphate, soluble phosphoric acid, and ammonia, are brought in contact with one another, the double insoluble phosphate of ammonium and magnesium (MgNH,PO,6Aq) is formed. While such a reaction is possible, it is highly improbable that it takes place to any extent. The double phosphate is a crystalline salt which only separates after a considerable time, and in the presence of a large excess of ammonia.