(1) Natural (organic)--the direct product. of animals or plants, such as farmyard manure, seaweed, green manure, fish guano, &c.

as

(2) Artificial (inorganic)-this term is used quite correctly of such manures superphosphate, nitrate of lime and others which are produced by processes of manufacture; it is also used, not quite correctly, of mineral manures such as mineral phosphate, potash salts and nitrate of soda, which are, strictly speaking, natural.

There are three forms of food which plants mainly require from the soil, nitrogen, potash and phosphates. Artificial manures, as a rule, supply only one of these forms. Each class-nitrogenous, potassic and phosphatic-comprises several kinds of manures which differ in their action. Thus in the nitrogen class, nitrate of soda is quicker in its action than sulphate of ammonia, and in the phosphate class superphosphate is quicker than raw phosphate. Or one kind may be more suitable to a certain crop than another, as, in the potash class, sulphate of potash is better than kainit for potatoes, and in the phosphate class basic slag is usually better for grassland. Guidance is given as to the average quantities required by different crops. Three points require to be noted:

1.-If a plant is stinted in one of its requirements, even though other requirements are abundantly provided, the result will be little better than if it had been equally stinted of all.

2. It is equally wasteful to use too much as too little manure. The right amounts will lie somewhere in the neighbourhood of what is here given; the actually correct amounts can only be learned by experience and by trial.

The

3.-Costs, both one's own and those given in records of trials, must be studied. dressing which produces the highest yield is not always the most economical.

Of hardly less importance than the selection of manures is their distribution. Whatever amount of manure is employed, care should be taken to spread it equally over the soil. Artificial manures are easier to spread evenly when they are fine and free from lumps. It may be necessary to pass the material through a quarter-inch riddle, breaking all the lumps that fail to go . through. Some manures change into hard lups if stored for some months. This is one reason why it is seldom desirable to store manures for a long period. If this

has to be done, the addition of a small proportion of peat-litter dust or sawdust will help to keep them from caking. One often. sees artificial manure being sown containing lumps as large as peas, and sometimes as large as walnuts. Not only does the presence of lumps prevent much of the crop getting its air share of the dressing, but the spots on which the lumps fall are actually poisoned, so that the plants are weakened or killed outright.

Where possible, manures, especially the slower acting manures, should be thoroughly mixed with the soil. For instance, where artificials are being applied to a corn crop, they should be applied at seed time, so as to get the benefit of the subsequent harrowing.

NOTICES OF BOOKS.

Practical Physical Chemistry, by ALEXANDER FINDLAY, M.A., D.Sc. Pp. XVI. + 298. Fourth Edition. London: Messrs. Longmans, Green & Co., 39, Paternoster Row, E.C.4. 1923. 7s. 6d. net.

The first edition of Prof. Findlay's indispensable Practical Physical Chemistry appeared in 1906, and the third in 1914. Since the latter date the demand for the book has been met by the printing of new impressions.

Nearly a decade has elapsed since the subject matter has been revised, and hence, in the latest edition, he includes many alterations and extensive additions, yet the general character of the book as a student's laboratory companion remains unaltered.

New matter has been introduced, dealing with Cottrell's Ebullioscopic Method for determining Molecular Weights, and accounts of the Abbe Refractometer and Hilger's (constant deviation) Wave-length Spectrometer are also included.

Another important addition is a chapter containing a very suitable set of experiments illustrating some of the more striking properties of the colloidal state of matter.

It is now generally recognised that prac tical physical chemistry must form a part of a general chemistry curriculum, and the appearance of the present new edition should enable Prof. Findlay's volume to retain its popularity among both students and lecturers.

Kelly's Directory of the Chemical Industries. Pp. XXXI. + + 903. 1923. Kelly's Directories, Ltd., 186, Strand, W.C.2. 30s.

Information is given concerning chemical manufacturers, manufacturing chemists, wholesale druggists, drysalters, chemists and drug stores (wholesale and retail). Full lists of the trades comprised will be found in this book.

The sections of Kelly's Directory of the Chemical Industries, 1923, include:-An alphabetical arrangement of the names in the towns and villages under each county, with the populations; a general classification of trades for London and its suburbs, i.e., classified lists of profession and trades with the names arranged alphabetically of those engaged therein; a similar classification for the rest of England, Scotland and Wales; the names for the principal towns of Ireland, arranged under towns and trades; and the names of the Channel Islands and the Isle of Man arranged under towns.

Another feature is the list of proprietary brands and articles which gives the makers' name and address after the name of the articles.

It is very apparent that many alterations have been necessary, and it need hardly be pointed out that out-of-date directories are often the cause of much inconvenience and irritation. This applies to those for the chemical industries as well as others.

Report of the Oxygen Research Committee. Pp. VII. + 177; with 43 text figs. and 6 plates. 8s. 6d. net. By post 8s. 9d. Published by H.M. Stationery Office for the Dept. of Scientific and Industrial Research.

This report describes certain aspects of the work of the Oxygen Research Committee since its appointment in 1919. It deals chiefly with the technical difficulties which have hitherto restricted the commercial utilisation of liquid oxygen and liquid air, and describes in particular recent improvements in the methods of handling the liquefied gases on a practical commercial scale. The work of the Committee has been carried out principally in the Heriot Watt College, Edinburgh, and the Air Ministry Oxygen Laboratory.

The subject matter of the report is arranged under the following headings:

Part I.-The Storage of Liquefied Gases: The vacuum vessel; the physics of the vacuum vessel; experimental analysis of heat entry; adsorbents and adsorption.

Part II.-The Manufacture of Melal Vacuum Vessels for Liquefied Gases: Defects of containers and vaporisers; improvements in the design of vaporiser receptacles; the assembly of vacuum vessels; the testing of vacuum vessels; the problem of evacuation; evacuating plant.

Part III.-Vacuum Vessels in Use: Glass vacuum flasks; the transference of liquefied gases; some results of the periodic testing of vaporisers; decay of vacua in metal flasks.

Part IV.-The Transport of Liquefied Gases and Compressed Gases: Protection and support of containers in transit; losses during transport; railway regulations for the transport of liquid air; the transport of compressed oxygen.

Appendix.-Physical Data.

Index.

Elementary Chemical Calculations, by MARTIN MEYER, PH.D., College of the City of New York. Pp. VI. + 131. 1923. Oxford Book Company, 175, Fifth Avenue, New York, U.S.A.

187592-Howard, H.-Process for the production of hydrogen sulphide.

192703-Soc. d'Etudes Chimiques pour l'Industrie. Process for the manufacture of from cyanamide.

urea

PUBLICATIONS RECEIVED. Bulletins issued by the U.S. Department of the Interior, Bureau of Mines:

The Electrothermic Metallurgy of Zinc, by B. M. O'HARA. Pp. VI. + 106.

Timbering of Metal Mines, by E. A. HOLBROOK, RICHARD V. AGETON, and HARRY E. TUFFT. Pp. VII. + 72.

Water-Gas Tar Emulsions, by W. W. ODELL. Pp. IV. + 51.

Leaching Nonsulphide Copper Ores with Sulphur Dioxide, by CHARLES E. VAN BARNEVELD and EDMUND S. LEAVER. Pp. V. + 91.

New Patents

THIS list is specially compiled for The Chemical News, by Messrs. Rayner & Co., Registered Patent Agents. of 5. Chancery Lane, London, from whom all information relating to Patents, Trade Marks, and Designs can be obtained gratuitously.

Latest Patent Applications.

25111-British Cellulose & Chemical Manufacturing Co., Ltd.-Treatment of cellulose derivatives. Oct. 9.

25328-Crundall, S. F. W.-Production of titanium compounds. Oct. 11.

25274-Thorn, I.-Process of hardening products of condensation from phenols and aldehydes. Oct. 10.

25478-Hoffman la Roche & Co., Akt-Ges. F.Manufacture of emulsions of bismuth salts. Oct. 12.

Specifications Published this Week.

182803 Ges Fur Kohlentechnik.-Process and apparatus for separating ammonia and benzol hydrocarbons from coal distillation gases.

Lignone sulphonic acids; pulp, preparation of ---Wood and like lignified materials are resolved by treatment at 100-110° C. with a strong aqueous solution of sulphurous acid which is originally substantially free from sulphuric acid. Preferably the process is carried out in a digester lined with acid-resisting cement, and the materials under treatment are rapidly agitated. In an example, wood prepared as for the bisulphite process is treated with six times its weight of a seven per cent. solution of sulphurous acid purified from sulphuric acid. The mass is heated with open steam for six hours; then steam at a temperature of 105-110° C. is employed for a further ten hours to complete the resolution. The liquor containing the lignone derivatives may be evaporated to dryness, preferably under reduced pressure, or prepared in concentrated form for transport. These derivatives are stated to be different from those contained in sulphite-cellulose liquor.