that at the period when growth was temporarily arrested the so-called leguminous nodules were absent or only in an incipient state, whilst those plants which were growing properly possessed nodules, and that the older and larger the nodules, the better was the development of the plant. These nodules are full of bacteria, and a series of experiments was made, in which to peas growing in soil containing no combined nitrogen there was added, in some cases, an aqueous extract of fertile soil, in others the same extract after sterilisation, and in others again no such addition was made. It was found that the nodules and the thriving of the plant could be produced or prevented at will by the addition or exclusion of micro-organisms.

The growth of lupines on soil containing no combined nitrogen was also investigated, and it was found that they would never attain a satisfactory development when exposed to the same opportunities of receiving germs from the air that enabled some of the peas to thrive; hence it was inferred that the bacteria which occur in the root nodules of lupines are different and less widely diffused than those occurring in peas. This view was supported by the facts that the nodules are different in shape and position on the two plants and contain micro-organisms of obviously different appearance, and also that lupines do not thrive on heavy or rich soil. It was put to the test by growing lupines in sand containing no combined nitrogen, and treating one part of them with an aqueous extract of the soil of a lupine field, a second part with an extract of a clay-marl containing humus and not growing lupines, and leaving a third part without any such addition. All three parts exhibited a period of arrested growth, then the first part started growing and showed nodules like ordinary lupines, the second part showed traces only, and the third part showed no traces of nodules at all.

Of other plants examined, Serradilla (Ornithopus sativus) behaved like lupines, whilst vetches and beans (Vicia faba) like peas developed best when treated with extract of rich soil; red clover gave no decided result. It thus appears that the Papilionacea are not dependent on the soil alone for their nitrogen, but that they can make use of the free nitrogen of the air, and that the root nodules and the microorganisms in them are in close and active relationship to the nourishment and especially to the assimilation of nitrogen by these plants. It must not, however, be inferred that the combined nitrogen of the soil is of no importance to them, for Hellriegel found in some experiments that they could make use of nitrates; although it seems questionable whether nitrates could produce a normal development if microorganisms were absolutely excluded.

Notwithstanding these researches, it is stated in the article to be still an open question whether the root nodules can change free nitrogen into nitrogenous compounds, although the growth of Papilionacea is strongly recommended as a means of increasing the combined nitrogen on the farm. To this same end, irrigation by brook and river water is recommended, as a great part of the combined nitrogen dissolved in the water is retained in the form of plant substance.

The second section treats of the ways in which combined nitrogen may be set free and lost, namely: (1) during germination; (2) in

the processes that go on in the animal body (both of which ways have been disputed); (3) during the putrefaction of nitrogenous substances; (4) during the decomposition of organic manures in the soil, especially when it is too strongly aërated by drainage, and nitrification consequently goes on too actively. This section also gives numerous directions for avoiding loss of combined nitrogen in the keeping and employment of manures. H. H. R.

Manuring Experiments on Oats. By K. MÜLLER (Bied. Centr., 1888, 103-107). The experiments seem to show that an oat crop following wheat after sugar-beet is grateful for phosphatic and nitrogenous manuring, even when the roots have been excessively manured with phosphates. Chili saltpetre alone produced an increase in grain and straw, the largest increase of grain being caused by the saltpetre in combination with precipitated phosphate, and the lowest by the saltpetre and superphosphate, the greatest increase in straw was produced by an inverted order of phosphates, basic slag holding a middle place in both cases. Placing the expense of manures against the increase in crop, it appeared that saltpetre was the most renumerative, whilst superphosphate and saltpetre together were applied at a loss.

E. W. P.

Increase in Yield of Crops by Nitrogenous Manures. By P. WAGNER (Bied. Centr., 1888, 78-96).—The author draws his conclusions from experiments made by himself, by Märcker, and others; it does not seem that the addition of saltpetre to leguminous crops is of any value, as the increase in yield is so very little, in fact, in some cases there appears to be a decrease in the yield, as the quantity of saltpetre increases. On the other hand, this manure is of value to straws and roots. Employing E. Lierke's tables, Wagner shows how varied is the money value of saltpetre with the different crops in cultivation, and the many circumstances which militate against the complete and successful action of nitrates; to obtain the best result all the necessary plant food must be present in full quantities, to say nothing of want of rain and warmth. The variations in the yield of grain or straw are fully entered on, as well as the causes of such variations. Ammoniacal manures are frequently unsatisfactory, although theoretically the quantity of nitrogen added may exceed that which would be contained in a dressing of nitrate; this probably arises from the fact that the conversion of the ammonia is so slow that the plants do not obtain a sufficiency of nitrate within the requisite time, consequently being "hungered" they are unable to make full use of the other plant foods; it is on this account that ammoniacal manures should be applied to the soil some time before the seed is sown, so that there may be a sufficiency of nitrates present to allow of full, rapid, and unhindered growth. E. W. P.

Manurial Action of the Free Lime in Basic Slag. By E. JENSCH (Bied. Centr., 1888, 12-16).—The activity of basic slag on soils poor in lime has often led to the free lime in the slag rather than the phosphate being regarded as the active agent. To examine this question six sets of experiments were made with oats grown in pots. A loamy

soil was chosen, and it was used both in its natural state and also after having been treated with dilute hydrochloric acid for some time and then washed. The manures employed were (1) basic slag meal in its original state; (2) basic slag meal which had been treated with sugar solution to remove free lime; (3) lime, and (4) potassium nitrate which was added uniformly to all the pots. The results of the experiments showed that the phosphate in slag from which the free lime had been removed gave nearly as good a yield as in that which still contained free lime, and that although a certain amount of benefit cannot be denied to the free lime, still the increased yield was chiefly due to the phosphate. H. H. R.

Analytical Chemistry.

Filtration Apparatus. By F. ALLIHN (Zeit. anal. Chem., 26, 721). The stem of the funnel has a bulbous expansion, which is ground into the neck of a thick-walled flask. This has a side-tube for connection with the air-pump. M. J. S.

Improved Form of Nitrometer. By G. LUNGE (Ber., 21, 376377). The improvement consists in substituting Friedrich's patent diagonally bored stopcock for the ordinary three-way stopcock of the nitrometer. W. P. W.

Estimation of Iodine. By N. McCULLOCH (Chem. News, 57, 4548).-Manganic oxide suffers slight reduction in presence of iodine (compare Abstr., 1887, 1141), and therefore titration of iodine by means of alkaline permanganate is inaccurate, and cannot be employed for the determination of iodine in presence of a chloride or bromide, although the latter are not oxidised under the conditions. Hydrogen peroxide is also unsuitable for the purpose. The author therefore proposes to eliminate the chloride and bromide by a process described in the paper in which the mixture containing the chloride, bromide, and iodide is heated with permanganate and strong sulphuric acid, the first two elements are driven off as hydrogen chloride and bromide respectively, whilst the whole of the iodine is oxidised to iodic acid. The solution is diluted, filtered, reduced by means of sulphurous acid, and the iodine determined either by precipitation as silver iodide, or by titration with permanganate in presence of free sulphuric acid and hydrocyanic acid; the latter forms colourless cyanogen iodide with the iodine set free by the sulphuric acid, which would otherwise mask the end reaction. This method of titration is free from the error of reduction of manganic oxide referred to above, and also from the inconvenience of the precipitated manganic oxide accompanying the use of alkaline permanganate. It cannot, however, be used in presence of hydrobromic acid or of the reducing salts of copper, iron, &c.

D. A. L.

into water.

Indirect Determination of Fluorine. By S. BEIN (Zeit. anal. Chem., 26, 733-736; from Rep. anal. Chem., 6, 169).-The fluorine is expelled as silicon fluoride by heating the substance with powdered quartz and sulphuric acid, and is driven over by a stream of dried air The fluoride and the quartz sand (12 parts) must be very finely ground and intimately mixed. The mixture is placed in a dry flask having a cork through which pass a tube for the admission of dried air, the tube of a separator bulb containing sulphuric acid, and a tube for conveying the gases into water. The last has the outer limb widened. For 1 gram of calcium fluoride, 50 c.c. of sulphuric acid is added and the flask is heated for three hours at 165° with occasional shaking. A further quantity of acid is then added, and the heating and shaking are continued as long as the gas bubbles produce any precipitate. After collecting and washing the silica by suction, it may be at once ignited without previous drying. One part corresponds with 5 494 parts of fluorine. M. J. S.

Estimation of Selenium. By H. N. WARREN (Chem. News, 57, 16). See p. 435.

Estimation of Nitrites. By A. VIVIER (Compt. rend., 106, 138140). The apparatus is similar to that used in the estimation of nitrites and nitrates by Schloesing's method. The air is first expelled by boiling a small quantity of water in the flask, and the solution of the nitrite is introduced, followed by a solution of carbamide, and finally by dilute sulphuric acid. A current of carbonic anhydride is passed through the apparatus during the whole operation. The mixture is gradually heated and finally is boiled for several minutes, the gas which is evolved being passed through potash solution to absorb carbonic anhydride, whilst the nitrogen is collected and measured. Care must be taken to expel the nitrogen from the flask at the close of the operation by the current of carbonic anhydride. The volume of nitrogen obtained is double that existing as a nitrite. C. H. B.

Free Acid in Superphosphates. By W. W. MELLON (J. Soc. Chem. Ind., 6, 803-805).—The average amount of free acid found in 485 samples of manures of various kinds examined was equal to 8.54 per cent. H,PO、; the highest being 16:36 per cent. and the lowest 2.36 per cent. The results of some experiments are given which show that the amount of free acid and soluble phosphate is affected by the method of extraction adopted, and by the strength of the acid used to decompose the phosphate. The free acid always present in manures seems to consist mainly of phosphoric acid with smaller amounts of hydrofluosilicic acid, hydrofluoric acid and (occasionally) sulphuric acid. The latter was found only in damp samples containing a large amount of free acid. The presence of free hydrofluosilicic and hydrofluoric acids in manures seems to have escaped observation; in the ordinary course of manure analysis, in which the moisture is determined by heating the sample for several hours in the water-bath, they are volatilised and reported as moisture. The average amount of volatile free acids found in 14 samples was

equal to 2:30 per cent., H,PO, the highest being 3.96 per cent. and the lowest 0-96 per cent. They were estimated by evaporating a solution of the manure to dryness in a platinum dish, the residue was dissolved in water to which a known amount of standard acid had been added, and the solution titrated with standard alkali. The loss of free acid on evaporation equals the total volatile acidity calculated as H,PO. The amount of free hydrofluosilicic acid found in the 14 samples tested, comprised about two-thirds of the total volatile acidity. The estimation was made by evaporating to dryness a solution of the manure to which some potassium sulphate, neutral to methyl-orange, had been added, the residue being dissolved in standard acid and titrated as before. The increase in the amount of free acid as H,PO, after evaporation with potassium sulphate, as compared with the amount found on evaporating the solution per se, is equivalent to the free hydrofluosilicic acid present.

D. B.

Determination of Arsenic as Pentasulphide. By L. W. MCCAY (Amer. Chem. J., 9, 174-180).-The tedious precipitation of arsenic pentasulphide according to the directions of Bunsen may be replaced by a very simple, rapid and efficacious method, namely:the solution containing arsenic acid equivalent to about one to three tenths of a gram of the pentasulphide, is placed in a bottle of 200 c.c. capacity provided with a well-ground stopper; the bottle having been almost filled with freshly boiled water, and the contents saturated with hydrogen sulphide, it is closed, the stopper tied down, and the whole placed in a water-bath for one hour. The precipitate is most easily removed from the bottle, and, the air having been excluded, contains no free sulphur, and does not require to be washed with alcohol and carbon bisulphide. When arsenious acid is treated with hydrogen sulphide in presence of air, but otherwise as above described, it is converted into the trisulphide, no pentasulphide being formed.

H. B.

Quantitative Analysis by Electrolysis. By A. CLASSEN (Ber., 21, 359-369). A simple form of rheostat is described which affords the means of carrying on simultaneously with one battery eight determinations of different metals requiring different strengths of current, and a number of very concordant results obtained by its use are detailed. A new form of voltameter is also described, consisting of a vertical, stoppered, graduated tube expanded at its lower portion into a cylindrical chamber containing the platinum electrodes, which is connected to a second vertical pressure tube by means of india-rubber tubing. This arrangement renders it possible for the gas in the voltameter to be measured at the atmospheric pressure. A description is also given of a stand for the support of the platinum dish forming the cathode and of the anode, whose chief point of novelty consists in the substitution of glass for brass for the material of the rod which supports the arms.

Estimation of Copper in the Presence of Arsenic.-In the presence of more than 0.2 per cent. of arsenic, it has been found impossible in practice to employ the electrolytic method for the deposition of copper

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