osition to the attention of American cement manufacturers as early as June, 1904 A number of laboratory tests do seem to indicate that the iron ore cement is proof against the corrosive action of sea water, but laboratory tests are not "engineering practice," and it is with this paragraph of the bulletin. that THE CHEMICAL ENGINEER has fault to find. It is by no means certain that Portland cement mortar, properly proportioned, mixed and placed, will not withstand the corrosive action of sea water. Dr. Rudolph Dyckerhoff, the distinguished German cement chemist, is the authority for the statement that concrete cubes, placed in the sea at Copenhagen in 1862, and taken out in 1902, were found to be entirely intact. The committee on the action of sea water on hydraulic cements of the German Cement Manufacturers' Association reported, at the last meeting of this association, that experiments begun in 1894 seemed to show that there was no marked difference in the behavior of cements, when used in sea water, between those containing 5 per cent alumina and those containing 8.5 per cent. This committee did find that the interior surface of concrete cubes which had been in sea water since 1890 showed upon analysis 5 per cent less lime and 2 per cent more magnesia and sulphuric acid each than did the interior portions. In spite of this chemical reaction, however, the exterior surface was so hard that it was difficult to chisel it off.

In the face of such evidence, it is rather hard to believe that the mere fact that disks of neat Portland cement molded under pressure failed to stand immersion in boiling calcium sulphate solution is proof that Portland cement cannot be used in sea water. We have repeatedly contended that tests based purely upon theoretical considerations are always liable to lead to false conclusions. No test is entirely reliable until its results have been compared with the practical working of the material.

We do not think that good engineering practice concerns itself with limiting the alumina in Portland cement to be used in sea water to a figure below that ordinarily met with in American Portland cement. Good engineering practice does see that the cement to be used shall conform to certain well tested specifications as to fineness, setting time, constancy of volume, tensile strength, magnesia and sulphuric acid. It also specifies the proper use of the cement; the careful proportioning of the aggregates to eliminate voids, and the thorough mixing and tamping of the concrete to secure homogeneity and density. Having done this is feels securer as to the lasting qualities of the work than it would if it had purchased untried cement under freak specifications.

Dust Explosions

In view of the recent disastrous explosions in the bituminous coal field. at Monongah, W. Va., and at Jacob's Creek, Pa., Prof. Peckham's paper, begun in this issue of THE CHEMICAL ENGINEER and completed in our

next, will be read with interest by many American chemists and engineers. Dust is now recognized to be very explosive when suspended in air and while it shows none of these properties en masse, when the separate particles are surrounded by air a powerful explosive is formed. The energy released by an explosion is dependent on the heat units it contains, coal dust is therefore capable of an explosive force of nearly four times that of gun-powder. We do not mean by this that a pound of coal dust rammed into a hole is four times as powerful an explosive as a pound of gunpowder, because in order to convert it into an explosive it would be necessary to confine also in this hole and ultimately mixed with the coal two and two-thirds pounds of oxygen. In the case of dust suspended in air, the oxygen is present and a perfect explosion is formed.

Disastrous dust explosions have occurred in many industrial plants, attended with both loss of life and property. The study of the causes which lead up to them is therefore incumbent upon manufacturers of combustible substances from which dust is given off in the making. Several serious explosions of coal dust occurred when pulverized coal was first used as a fuel for cement burning. The subject of coal dust explosions therefore received the attention of the cement technologists with the result that few explosions have occurred in the last four years. The remedy in this case resolved itself into better ventilation of the coal grinding room, the introduction of encased grinders, careful electric wiring and incandescent lighting and the instruction of the workingmen as to the dangers of naked flame lamps when working in the coal mill or in bins in which pulverized coal had been stored.

A careful study of conditions will usually show what steps should be taken to effectively guard employes against death or injury from dust explosions. The manufacturer who is not willing to take the steps necessary to ascertain how to avoid dust explosions is certainly very callous as to the welfare of his fellow man and for the control of such we recommend an employer's liability act which will force him as a safeguard to his pocketbook to guard the lives and limbs of those who are unfortunate enough to have to work for them.

The largest cadmium works in the world are in Upper Silesia. The material used is either the flue dust or zinc dust collected during the first 11⁄2 or 2 hours of the distillation in the sheet iron cones attached to the adapters, and which contains up to 6% (less frequently up to 8%) of cadmium, or the zinc dust deposited in the first portion of the dust chambers which form the continuation of the Kleeman and Dagner adapters. This dust contains 1.2 to 3% of cadmium.

CHEMICAL SOCIETIES.

AMERICAN CHEMICAL SOCIETY.-M. T. Bogert, Pres.; Charles L. Parsons, Sec'y, Durham, N. H.

SOCIETY OF CHEMICAL INDUSTRY, NEW YORK SECTION.-George C. Stone, Pres.; H. Schweitzer, Sec'y, 128 Duane St., N. Y. City. NEW ENGLAND SECTION.-Henry Howard, Pres.; Alan A. Claffin, Sec'y, Box 1189, Boston, Mass.

WESTERN ASSOCIATION OF TECHNICAL CHEMISTS AND METALLURGISTS.-W. G. Swart, Pres.; H. C. Parmalet, Sec'y, P. O. Box 1421, Denver, Colo.

AMERICAN SOCIETY FOR TESting MaterialS.-Charles B. Dudley, Pres.; Edgar Marburg, Sec'y, Univ. of Penn'a, Philadelphia, Pa.

AMERICAN ELECTROCHEMICAL SOCIETY.-C. F. Burgess, Pres.; J. W. Richards, Sec'y, Bethlehem, Pa.

AMERICAN LEATHER CHEMISTS' ASSOCIATION.-F. H. Small, Pres.; W. K. Alsop, Sec'y., 26 Ferry St., New York, N. Y.

CHEMICAL SOCIETIES.

For the benefit of many of our subscribers who are anxious to know, that body to have had, at the time of the Chicago meeting, a membership of 3,389, a net gain of 310 during 1907. Of these members, however, only 2,289 were not in arrears for dues. The report of the librarian shows the society to have published during the past year 3,046 pages of abstracts, 1,624 pages of original papers, 73 pages of book reviews, 73 pages of reviews of various branches of chemistry and 92 pages of proceedings. The treasurer's report shows the total receipts from all sources during the year to have been $33,275.25 and the expenditures $27,248.89. Of this latter the printing of the journal and chemical abstracts amounted to $12,788.31 and the abstractors were paid $3,578.29. The treasurer had a balance on hand December 16, 1907, of $11,083.10, of which $7,444.48 was in the Knickerbocker Trust Company.

For the benefit of many of our subscribers who are anxious to know the dues of the various chemical societies are given below:

None of the above societies except the Society of Chemical Industry charges any initiation fee, the fee in this case being $4.35. All of these societies except the American Society for Testing Materials publish a journal. The latter body issues an annual volume of proceedings containing the papers and discussions presented at their annual meeting.

At the meeting of the Society of Chemical Industry, New York Section, held February 21st, at the Chemists' Club, New York City, the following papers were read: "Manufacture of Ferro-Chrome in the Electric Furnace," Roland Carlberla; "Injury to Vegetation by the Fumes from Chemical Factories," Charles Baskerville; "The Preparation and Uses of Anhydrous Tetrachloride of Tin," E. A. Sperry; "The Influence of Sunlight on Paints and Varnishes," Maximilian Toch.

CORRESPONDENCE.

Pressure Regulator.

How can I regulate the pressure of air delivered to a blast lamp? The air is from a pressure blower and varies between one and two pounds' pressure, according to the work being done in the foundry. This makes the blast very unsteady?

The following arrangement, the description of which is taken from the sheets of Mr. Meade's forthcoming book on "The Design and Construction of Small Chemical Laboratories," will be found to answer perfectly. This consists of a cylinder or bottle stoppered with a 2-hole cork or rubber stopper. (See illustration.) One of the holes is left open and through the other passes a T-tube, one end of which dips into a little mercury in the bottle. The pressure is regulated by the distance into the mercury which the T-tube dips. The upper branches of the T-tube are connected, one with the blast lamp and the other with the air mains.

Monox.

What is "monox," how is it prepared, and for what is it used?

"Monox" is a trade name for silicon monoxide. Two papers concerning it and its uses were read at the last meeting of the American Electrochemical Society by Dr. H. N. Potter, the inventor of a process for its manufacture. The latter consists of heating silica in the form of glass makers' sand with some reducing agent such as coke, graphite, siloxicon, silicon carbide, carborundum, etc., in an electric furnace. The silica

monoxide escapes from the furnace into a drum under reduced pressure where it cools and is deposited on the walls and exposed surfaces of the latter.

Monox may be used in the form of a screen coated with it to sterilize or filter air. It has the power of thickening fluids with which it is mixed and hence it is proposed to use it as a paint, particularly for brickwork and structural iron. It is also proposed to use it in printers' ink, as it makes the ink lay well and dry with a dead, lustreless black, and also to employ it in ceramics, as a heat insulator and as a lubricant.

Stannic Chloride.

Can you give me the most recent table for calculating the percentage of stannic chloride (fairly pure) in a solution from specific gravity?

The following table recently appeared in the Chemiker Zeitung and was prepared by P. Heerman, who used for his experiments stannic chloride containing about 0.1% impurities. The degrees Baumé are German standard at 17.5° C.:

Will you give me a method of testing shellac?

Mr. H. Endemann gives the following method for testing shellac (J. Frank. Inst.. CLXIV, 286): Mix two grams of the shellac to be tested. with 4 cc. of alcohol and 10 grams of sand which has been ignited, washed in hydrochloric acid and dried. Add 10 cc. of hydrochloric acid and evaporate to dryness or a water bath. Repeat this evaporation to dryness twice and bake at 105° C. for two hours. Cool, add 20 cc. of alcohol (95%)