cultur-Chemie," vol. 2; and F. Schulze, "Journ. f. prakt. Chem.," vol. 47, page 241. The experiments for ascertaining the absorbing power of a soil may be made by Liebig's method, described in "Annal. d. Chem. u. Pharm.," vol. 105, page 113.

V. ANALYSIS OF MANURES.

§ 260.

I SPEAK here simply of the manures supplied by the urine and excrements, and the blood and bone of animals. The examination of manures has chiefly a practical object, and demands accordingly simple methods. The value of a manure depends upon the nature and condition of its constituents, of which the following are the most important: organic matters (characterized by their carbon and nitrogen), salts of ammonia, nitrates, phosphates, silicates, sulphates, and chlorides of alkalies or alkaline earths (potassa, soda, lime, magnesia). Respecting the condition in which the ingredients of manures may be deemed to exercise the most effective and favorable action on the soil, our views are much less clear; indeed, it is obvious that a universally applicable and valid rule cannot well be laid down in this respect; since the agriculturist sometimes wishes a manure containing most of its constituents in a state of solution, which will accordingly exercise a speedy fertilizing action,* and sometimes one which will only gradually supply the soil with the substances required by the plants.

I will here give 1, the outlines of a general method of examining manures; 2, methods of analysing guano and bone manures.

A. ANALYSIS OF MANURES IN GENERAL.

§ 261.

Mix the manure uniformly by chopping and crumbling, then weigh off successively the several portions required for the various analytical processes.

1. Determination of the Water.

Dry 10 grammes in the water-bath, and determine the loss of weight (§ 28). It is rarely necessary to make a correction on account of the carbonate of ammonia which escapes with the water.†

2. Determination of the total Amount of fixed Constituents.

Incinerate, at a gentle heat, a weighed portion of the residue left in 1, in a platinum dish (§ 250, 2), or in a large platinum crucible placed in an oblique position, and weigh the ash.

3. Determination of the Constituents soluble in Water, and also of those insoluble in Water.

Digest 10 grammes of the fresh manure with 300 c.c. of water, pass

* This sort of manure may, however, prove injurious to tender plants, if applied in too large quantity, without proper dilution with water, and in dry weather.

The determination of the carbonate of ammonia is best effected by drying the manure in a little boat inserted into a tube; the tube is heated to 212° F., in the wateror air-bath, a current of air being transmitted through it, by means of an aspirator; the air on entering is made to pass through concentrated sulphuric acid, the air passing out through two U-shaped tubes containing standard oxalic acid. After drying, the quantity of ammonia expelled, which has combined with the oxalic acid, is deter mined (§ 99, 3).

the liquid through a weighed filter (§ 50), wash the residue, dry at 212° F., and weigh. The weight found expresses the total quantity of the substances insoluble in water, and the difference-after deducting the water found in 1-gives the amount of the soluble constituents. Incinerate now the insoluble residue, and weigh the ash; the weight of the ash expresses the total amount of the fixed constituents contained in the insoluble part, and the difference between this and the ash in 2 gives the total amount of fixed constituents contained in the soluble part.

4. Separate Determination of the several fixed Constituents.

Dry a larger portion of the manure, and treat it by one of the methods given for the preparation and analysis of the ashes of plants. 5. Determination of the total amount of Ammonia.

Treat a weighed portion of the manure by Schlösing's method (§ 99, 3, b).*

6. Determination of the total Amount of Nitrogen.

Moisten a weighed portion of the manure with a dilute solution of oxalic acid in sufficient quantity to impart a feebly acid reaction; dry, and determine the nitrogen, in the entire mass or in a weighed portion, according to the directions given in § 187. Deduct from the total amount of nitrogen so found the quantity corresponding to the ammonia and the nitric acid; the difference shows the quantity of nitrogen contained in the organic substances. It is generally sufficient, however, to know the total amount of the nitrogen.

7. Determination of the total Amount of Carbon.

Treat a portion of the dried residue of 1 by the process of organic analysis. If the dried manure contains carbonates, determine the carbonic acid in a separate portion, and deduct the result from the total amount obtained by the organic analysis; the difference shows the quantity of carbonic acid formed in the latter process by the carbon of the organic substances.

8. Determination of the Nitric Acid.

Treat a weighed portion of the manure with water, and evaporate the solution, with addition of pure carbonate of soda to distinct alkaline reaction; filter after some time, then evaporate the filtrate to dryness, weigh the residue, and determine in a fractional part of it the nitric acid as directed § 149, II., a, a; or, if the presence of organic substances interferes with the application of this method, as directed § 149, II, a, ẞ or y.

B. ANALYSIS OF GUANO.
§ 262.

Guano, or the dung of sea-fowl, well known for its great fertilizing properties, not only varies very considerably in quality in the different islands from which our supplies are derived, but is often also fraudulently adulterated with soil, brick-dust, carbonate of lime, and other matters. Guano being an important article of commerce, it will be readily understood, therefore, why it should be made the object of chemical examination more frequently than other manures.

If the quantity of ammonia is only small, the decimal standard oxalic acid is used.

The guano is mixed as uniformly as possible, and that which is intended for analysis is put into a stoppered bottle.

18

1. Determination of the Water.

This is effected exactly as in § 261, 1. Genuine guano loses from 7 to per cent.

2. Determination of the total Amount of fixed Constituents. Incinerate a weighed portion in a porcelain or platinum crucible placed in a slanting position, and weigh the ash. Good guano leaves from 30 to 33 per cent. of ash, guano of bad quality from 60 to 80 per cent., and a wilfully adulterated article often even more. The ash of genuine guano is white or gray. A yellow or reddish color indicates adulteration with loam, sand, or soil. In the first stage of the process of incineration good guano, in its incipient decomposition by heat, emits a strong ammoniacal odor and white fumes.

3. Determination of the Constituents soluble in Water, and also of those insoluble in Water.

Heat 10 grammes of guano with about 200 c.c. of water, pass the solution through a weighed filter, and wash the undissolved portion with hot water, until the water running off looks no longer yellowish and leaves no perceptible residue when evaporated upon platinum foil; dry the residue, and weigh. Deduct the weight of the water and of the insoluble residue from the weight of the guano; the difference expresses the amount of the soluble constituents. Incinerate the insoluble part and weigh the ash; the difference shows the amount of the fixed soluble salts. With very superior sorts of guano, the residue insoluble in water amounts to from 50 to 55 per cent.; with inferior sorts, to from 80 to 90 per cent. The brown-colored aqueous solution of genuine guano evolves ammonia upon evaporation, emits a urinous smell, and leaves a brown saline mass, consisting chiefly of sulphates of soda and potassa, chloride of ammonium, oxalate and phosphate of ammonia.

4. The Determination of the several fixed Constituents; 5. The Determination of the total Amount of Ammonia; 6. The Determination of the total Amount of Nitrogen; 7. The Determination of the total Amount of Carbon, are effected by the methods given in § 261.

8. Determination of the Carbonic Acid.

Genuine guano contains only a small proportion of carbonates. If therefore a guano effervesces strongly when moistened with dilute hydrochloric acid, this may be regarded as a tolerably conclusive proof of adulteration with carbonate of lime.

9. Determination of the Uric Acid.

If it is wished to ascertain the quantity of uric acid which a guano contains, treat the part insoluble in water with a weak solution of soda at a gentle heat, filter, and acidify the filtrate with hydrochloric acid, to precipitate the uric acid. Collect the uric acid on a weighed filter, dry, and weigh.

As the manuring value of a sample of guano may be estimated, with sufficient accuracy, by the phosphoric acid and nitrogen which it contains, the analysis may be considerably shortened, and confined to the following processes:

a. Determination of Water (see 1).

b. Determination of Ash (see 2).

c. Determination of Phosphoric Acid.-Mix 1 part (1 or 2 grammes) of the sample of guano with 1 part of carbonate of soda and 1 part of nitrate of potassa; heat cautiously, dissolve the residue in hydrochloric acid, filter, add ammonia to the filtrate to alkaline reaction, then acetic acid until the phosphate of lime is redissolved; lastly-without previously filtering off the very trifling precipitate of sesquioxide of iron-acetate of sesquioxide of uranium, and determine the phosphoric acid as directed § 134, 1, c.

d. Determination of Nitrogen, by the method described § 187. As mixing the guano in the mortar with soda-lime would be attended with escape of an appreciable amount of ammonia, it is advisable to effect this operation in the combustion tube, with the aid of a wire (see § 176, fig. 104).

C. ANALYSIS OF GROUND BONES.

$263.

There are three sorts of bone powder.

I. The powder obtained by the grinding of fresh bones, which is generally very coarse.

II. The powder obtained by the grinding of more or less decayed bones.

III. The powder of bones which, previous to the operation of grinding, have been submitted to the action of aqueous vapors.

I. Is very coarse, and contains a relatively large proportion of fat and of gelatinous matter.

II. Is considerably poorer in organic substances.

III. Is much finer than I. and II.; it contains hardly any fat, and is still poorer in gelatinous matter than II.

1. Examine the powder, in the first place, by careful inspection, sifting, and elutriation, to ascertain the degree of comminution, and the presence of foreign matters.

2. Determination of the Water.-Dry a sample at 212° F.

3. Determination of the total Amount of fixed Constituents.-Ignite about 5 grammes, with access of air, until the ash appears white; then weigh the residue.

4. Determination of the fixed Constituents severally.-Treat the ash of 3 with dilute hydrochloric acid, filter off the insoluble portion (sand, &c.), and determine the sesquioxide of iron, lime, magnesia, and phosphoric acid in the solution as directed § 253.

5. Determination of the Nitrogen.-Ignite 0.5-0.8 grm. with sodalime (§ 187).

6. Determination of the Fat.-Exhaust 5 grammes of the sample (very finely pounded), by boiling with ether, and dry the residue at 230° F. The loss of weight minus the mixture found in 2, shows the amount of fat. By way of control, the ether may be distilled off, and the residual fat weighed, care being taken to leave no water under the fat.

7. Deduct from the total weight the collective weight of the fixed constituents, carbonic acid, water, and fat; the difference expresses the quantity of gelatinous matter contained in the analysed sample.

8. Determine the carbonic acid as directed § 139, II., e, a, bb.

D. ANALYSIS OF SUPERPHOSPHATES OF LIME.

$264.

To increase the efficiency of basic phosphate of lime as a manuring agent, it is often treated with a certain quantity of sulphuric acid, with addition of water. This treatment causes the formation of sulphate of lime and of acid phosphate of lime, soluble in water. If 2 equivalents of hydrated sulphuric acid are used to 1 equivalent of basic phosphate of lime, the decomposition is complete; if less sulphuric acid is used, the decomposition is not complete. If the decomposed moist mass is converted into a dry powder by addition of some indifferent body, the acid phosphate of lime remains soluble in water; but if wood ashes are used for the purpose, phosphate of potassa is formed, whilst part of the soluble acid phosphate of lime is reconverted to the basic state, and becomes insoluble in water. Manures prepared in the manner described, are called superphosphates; they are made from calcined bones, bone ash, precipitated phosphate of lime, coprolites, and also from the powder of fresh bones. The analysis of these preparations being intended not only to show the quantities of the several constituents contained in them, but to give information also with regard to the state of solubility of these constituents, and more especially of the phosphates, the analytical process is less simple than for guano and ground bones.

1. Dry about 3 grammes of the sample at 320° F. The loss of weight expresses, a, the moisture; b, the water of the gypsum.

2. Boil, in a dish, 10 grammes of the sample with water, let deposit, decant the fluid on to a filter, and repeat the process of boiling, with moderate quantities of water, until the decanted fluid no longer shows acid reaction. Dilute the aqueous solution so obtained to the volume of 250 c.c., and dry the residue at about 212° F.

3. Of the aqueous solution, which generally appears yellow from the presence of organic matter, measure off 3 portions, a and ẞ of 50 c.c. each; Y of 100 c.c.

Evaporate a in a platinum dish, adding, after some time, cautiously, thin milk of lime just to distinct alkaline reaction; proceed with the evaporation, dry the residue at 320° F., and weigh; ignite the weighed residue, and weigh again; the difference between the results of the two weighings expresses the quantity of organic matter in the aqueous solution. Boil the residue with pure lime-water, then with water, filter, precipitate the sulphuric acid from the filtrate by addition of a little chloride of barium, then the baryta and lime by carbonate of ammonia, and determine the alkalies as chlorides according to § 153, 4, a, ẞ (16). B. Precipitate ẞ with chloride of barium, and determine the sulphuric acid in the usual way (§ 132, I., 1).

y. Add to y an excess of carbonate of soda and a little nitrate of potassa, and evaporate to dryness in a platinum dish. Ignite the residue gently, then treat with water, rinse into a beaker, add hydrochloric acid, and apply a gentle heat until complete solution is effected. Add to the clear fluid, ammonia, then acetic acid in excess; filter from the phosphate of sesquioxide of iron, divide the filtrate into two equal portions, and determine in one the phosphoric acid, by means of solution of acetate of sesquioxide of uranium (§ 134, c), in the other the lime and magnesia as directed § 154, 4, b (31).