straw increases, so does the percentage of free gas. The conclusions which may be drawn from these last observations are that the thicker the crop stands on the land the poorer will be that land in free carbonic anhydride, because the temperature and the moisture are lower than those of a bare soil, consequently manures which increase the growth of the crop reduce the percentage of free gas. Further, the amount of gas found in the air of a soil must not be considered as a measure of the intensity of decomposition occurring in soils, nor of the quantity of organic matter present if the surfaces are different. E. W. P.

Nature of Nitrogenous Organic Matter of Soils. By R. WARINGTON (Chem. News, 55, 27-28).—In the author's experiments, indications of a very small quantity of soluble amide were obtained in the aqueous extract of a soil rich in nitrogen. The soil had been manured annually for the last 38 years with farmyard manure; it contained when dry 0.189 per cent. of nitrogen. The same sample of soil, after treatment with potassium carbonate, yielded an extract which did not contain amide bases or acids soluble in ether, but on treating the acidified extract with phosphotungstic acid it gave a precipitate containing nitrogen (compare Loges, Abstr., 1886, 96). In further experiments it is shown that cold hydrochloric acid removes from both surface- and sub-soils considerable amounts of nitrogenous organic matter, the amount increasing with the strength of the acid and duration of contact. Even when the same soil was treated four times successively there was no apparent exhaustion of this nitrogenous matter. Ammonia was found in the first extracts, but not sought for in the others. The strongest acid employed contained 5 vols. of hydrochloric acid solution per cent. Reference is made to Baumann (this vol., p. 82-84) and to Berthelot and André (ibid., 293-294). The results obtained by Julie (Abstr., 1884, 14131416) seem to indicate the synthesis of some such amides as those observed by Berthelot and André (loc. cit.). D. A. L.

Decomposition of Organic Matter in Soils. By E. WOLLNY (Bied. Centr., 1887, 1-11).—The changes which take place during the decomposition of organic matters used as fertilisers, show many points of interest. The fertility of soils depends much on them, and as some of them can be artificially directed, their study is of value.

Carbonic anhydride, water, ammonia, and free nitrogen are disengaged, and where there is free access of air nitric acid is produced, but it has been abundantly proved that nitrification is, partly at least, a physiological process, caused by micro-organisms; little is known of their action, but the presence of oxygen seems to be a necessary condition; the temperature is also an important factor; at 5° nitrification proceeds slowly, at 12° more rapidly, and at 37° it seems to have reached its most favourable stage. Moisture is also an aid to the process, provided it is not so abundant as to stop the pores of the soil and prevent access of air; light is injurious to nitrification, presence of acids stops it, and bases must be present to combine with the nitric acid formed. Soil treated with hydrochloric acid to remove its soluble constituents, yielded very little carbonic anhydride

with organic matter, but when a solution containing those matters was added to it, the production became normal; contrary to general opinion, lime was not found to hasten the decomposition of organic matter; weak solutions of sodium chloride and nitrate were favourable, but strong solutions were not, and the rapidity of decomposition was greatly facilitated by a minute state of division.

A table shows the rate of decomposition of many organic substances, from which it appears that bone meal, fish guano, and birds' excrement are in the first rank, the most difficult being leather and horn meal.

The nitrogen contained in different materials is known to vary in manurial value. The author thinks that which is present in humus and peat is of little worth, and should not add to the value of manure when, in the form of moss litter, it is a constituent of stable manure. The fat contained in certain manure materials aids decomposition; flesh and bone meals deprived of their fat decay more slowly than when it is left in them.

J. F.

Behaviour of Urea in Soils. By O. KELLNER and others (Bied. Centr., 1880, 812-813).-It is well known that fresh human urine destroys plants, although it is slightly acid, and therefore can be neutralised by the soil, also, that as soon as it has decomposed slightly and become alkaline, it is no longer harmful.

Experiments now prove that it is the urea which is not absorbed by the soil, but coming in contact with roots of plants, prevents absorption of water, and so causes drooping of the leaves. E. W. P.

Manuring with Thomas Slag and other Phosphates. By M. FLEISCHER, BRINCKMANN and others (Bied. Centr., 1886, 815-823).— The experiments which are here recorded were made on moorland soils, and with various crops (rye, potatoes, &c.), and all point out the great advantages obtained by the use of Thomas slag; they show that this and precipitated phosphates are equal in gross value, and that Thomas slag is superior in net value; that precipitated iron phosphate is far behind slag on moorlands, and that in those cases where there was no advantage in the first season, the effects showed themselves in the succeeding crop. E. W. P.

Manuring with Thomas Slag. By FITTBOGEN and SALFELD (Bied. Centr., 1887, 83-88).-Thomas slag, in conjunction with calcium humate and humic acid was employed as a manure in comparison with mono-, di-, tri-, and tetra-calcium phosphates, some of these being assisted by calcium humate; the seed employed was that of barley. The results were unsatisfactory, far less advantage being gained than in the previous year. There seemed to be no relationship between the quantity of manure used and the percentage of ash in the upper portion of the plants; but the percentage of phosphoric acid was increased by the employment of phosphates, and more especially when the calcium humate was added, still more so by the addition of humic acid in the free condition. Salfeld's experiments show that the effect produced by the slag is largely dependent on the character of the soil,

for with him, using nitre and kainite in addition, the results were good. E. W. P.

Manurial Value of Thomas Slag. By P. WAGNER (Bied. Centr., 1887, 31—41).—The author has given great attention to the utilisation of this bye-product in agriculture, and has made numerous experiments to ascertain its comparative value as tried against other phosphatic materials.

The composition of the slag explains its ready solubility, the phosphoric acid contained therein being supersaturated with lime, and when put into the soil in a state of fine division, the carbonic anhydride, the humic and other organic acids present readily combine with the lime and set free the phosphoric acid.

Experiments were made at Darmstadt Experimental Station, some in the open field with natural soil, others with the prepared earth in zinc cylinders, loam, calcareous soil, and sand deprived of lime; the plants were oats and barley, the slag being finely ground in some cases, coarse in others; the manure used for comparison was superphosphate from bone ash; tables show the effects of different quantities of phosphoric acid, but the net result is stated to be 1 part of soluble phosphoric acid in superphosphate equals 21 parts of finely ground slag and 56 of coarsely ground.

Three series of experiments were again made with other crops and mannres, of which a summary gives the following comparative results. Counting the increase yielded by superphosphate of 18.74 per cent. soluble phosphoric acid as 100, the other manures show— Superphosphate, 100; Peruvian guano, 30; bone meal, 10; ground coprolites, 9; three samples of Thomas slag of different degrees of fineness, 61, 58, 13.

The fineness of the ground slag has a very great effect on the yield, and the author recommends certain precautions to the buyers to secure fineness. It has been said that the presence of iron would prove injurious to the crops, but the author did not find such to be the

case.

The slag is recommended to be used on moorlands or humous soils, where it produces better results than on purely mineral soils; for meadows, potash salts should be added, and on mineral soils double the usual quantity of phosphoric acid. Sulphate of ammonia should not be added to the slag, as it is decomposed with loss of ammonia; where peat mould is available, a small quantity is recommended to be mixed with it. J. F.

Analytical Chemistry.

Indirect Determination of Chlorine, Bromine, and Iodine ty the Electrolysis of their Silver Salts, &c. By J. E. WHITFIELD (Amer. Chem. J., 8, 421-426).—The indirect estimation of any two of the halogens may be effected satisfactorily by precipitating both

together as silver salts, collecting on an asbestos filter, washing, drying at 150°, weighing, dissolving the residue in potassium cyanide, and either electrolysing the solution to determine the silver or precipitating the silver as iodide; again collecting on asbestos, washing, drying, and weighing. In a mixture of all three halogens, the iodine is first separated by known methods, and the chlorine and bromine indirectly estimated as described.

H. B.

Estimation of Sulphur in Soluble Slags. By E. D. CAMPBell (Chem. News, 55, 74). The slag is decomposed by means of hydrochloric acid with the addition of bromine, the mixture is gradually heated, and then boiled. The solution is filtered and the oxidised sulphur precipitated with barium chloride.

D. A. L.

Absorption of Nitric Oxide by Sulphuric Acid. By F. NETTLEFOLD (Chem. News, 55, 28-29).-The author treated different samples of guncotton and nitre with sulphuric acid and measured the nitric oxide evolved; on now adding more sulphuric acid and measuring again, absorption of nitric oxide was observed in all cases, the quantity varying with the substance employed, but never exceeding a few hundredths per cent. of the total nitric oxide. With pure nitric oxide, no such absorption was observed. The acid employed had a sp. gr. of 1.842. D. A. L.

Detection of Phosphorus by Mitscherlich's Method. ByMANKIEWICZ (Arch. Pharm. [3], 25, 32).-0·001 gram of phosphorus in 200 grams of 3 per cent. carbolic acid water does not give the characteristic phosphorescence, and so would be overlooked; with 0.002 gram even, the test fails; but with 0.005 gram it succeeds.

J. T.

Simplified Method for the Estimation of Phosphoric Acid from the Weight of the Molybdenum Precipitate. By E. THILO (Chem. Zeit., 11, 193-195), A. ISBERT (ibid., 223), and LAIBLE (ibid., 286). The reducing action of the filter-paper is adduced as a constant but variable source of error in estimating phosphoric acid by weighing the dried molybdenum precipitate, and as the mechanical removal of the precipitate from the filter cannot be effected without some loss, the author proposes and fully describes a method of dissolving the molybdenum precipitate in standardised ammonia, titrating any excess with standard acid, and calculating the percentage of phosphoric acid from the amount of ammonia required to dissolve the precipitate. As silica does not interfere with the working of the method, its previous removal is superfluous. For the precipitation of phosphoric acid, a relatively small excess of molybdate is sufficient.

Isbert has made experiments in the above direction, both with ammonia and soda, and with numerous indicators for the titration, but could not get concordant results. He points out that the molybdic precipitate always contains more or less molybdic acid, which of course affects the results; moreover the end reaction with the indicators is either indistinct or not visible. He suggests a method based on the determination of the ammonia in the precipitate.

Laible shows that the results obtained from the determinations of both ammonia and nitrogen in both the molybdenum precipitate and in ammonium magnesium phosphate, cannot be used as a basis for the calculation of the percentage of phosphoric acid, inasmuch as the percentage of ammonia in the molybdenum precipitate is not constant. In the case of the ammonium magnesium phosphate, when the precipitate is washed with water owing to its solubility the results are low; and on the other hand, when it is washed with ammoniacal water and dried, the results are also low, owing presumably to loss of ammonia while drying. D. A. L.

Determination of Phosphorus in Iron and Steel. By L. SCHNEIDER (Chem. Centr., 1887, 45).—If the solution of iron in nitric acid is not evaporated to dryness, and the dry mass strongly heated, the molybenum method always gives too low a percentage of phosphorus. The cause of this error is that the phosphorus is not completely oxidised to phosphoric acid by simple solution in nitric acid; a portion goes into solution as phosphorous acid, and so escapes precipitation with ammonium molybdate. It is necessary, therefore, to evaporate and heat the iron nitrate in order to complete the oxidation. G. H. M.

Determination of Phosphorus in Basic Slag. By C. BRUnneMANN (Chem. Zeit., 11, 19—20).-The author at the present time carries out his process as follows:-10 grams of the slag are digested with 50 c.c. of water; 100 cc. of hydrochloric acid, 50 c.c. of nitric acid, and 10 c.c. of strong sulphuric acid are added, and the whole is boiled for half to three-quarters of an hour. The hot liquid is poured into 400 c.c. of hot water in a litre flask; the calcium sulphate is dissolved by further diluting and shaking; the cooled mixture is made up to a litre, and the silica, sand, and carbon are allowed to subside. Of the clear liquid, 50 cc is evaporated until the hydrochloric and nitric acids are expelled; the sulphuric acid is neutralised by careful addition of ammonia; the whole is evaporated to dryness and heated to 110° to render the silica insoluble. The mass is rubbed up with 10 c.c. of strong nitric acid; 50 c.c. of hot water are added; the silica is filtered off, and the phosphoric acid is precipitated by molybdate as usual. By this method, the phosphorus of the iron phosphide is reported as phosphoric acid, which, in the author's opinion, is justified by the rapidity with which it oxidises in the soil. M. J. S.

Determination of Phosphoric Acid in Basic Slag. By G. LOGES (Chem. Centr., 1887, 229).-The author recommends that the slag should be attacked with concentrated sulphuric acid, avoiding oxidising agents. He considers that the phosphorus of the iron phosphide should not be converted into and reported as phosphoric acid, since, although it undergoes oxidation in the soil, its value as a manure is not equal to that of the ready formed phosphate.

M. J. S. Estimation of Silicon in Iron. By G. H. STRICK (Dingl. polyt. J., 262, 384).-2 grams of iron is dissolved in dilute sulphuric acid, and the solution evaporated to expel all water. The iron sulphate is then