June,
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T H E J O CR-YAL OF I.1-D C-ST R I A L A N D E.YGI.1-EERIA1-G C H E N I S T R Y .
paratus, which is self-acting and requires very little attention in its use, is being placed on the market by a London firm for the chemical treatment of water and trade effluents, in which the exact proportions of reagents are maintained, i t is claimed, notwithstanding any change which may occur in the rate of flow of the liquid under treatment. The apparatus is said to be adapted to deal with large quantities of liquid, and if constructed on a small scale may prove useful in other ways. The crude liquid to be treated passes under slight pressure through a pipe leading to the purifyint tank. A portion of the pipe being constricted a t one point like the Venturi tube allows the liquid to flow a t this point a t a greater velocity than in the full-sized portion; consequently, as the velocity increases, there is a corresponding decrease of pressure in the narrower portion, which is connected with two vertical pipes, each containing a float of a material heavier than water. A cylindrical vessel containing the reagent is attached to these floats by a lever, and the change of pressure is used as the power for setting the apparatus in action. When the apparatus is a t work, the liquid in the two vertical pipes stand a t levels depending upon the velocities of flow in the two portions of the Venturi tube, the difference of these two levels determining the amount of reagent entering the main stream. It is claimed by the manufacturers that under the most extreme conditions, the error in use will not exceed 1 . 7 per cent. ~
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TElE STERILIZATION OF POTABLE WATERS. In a paper on the “Sterilization of Drinking Waters by the Action of Ozonized Oxygen and of Chlorine Compounds in the Nascent State,” presented before the Paris Academy of Sciences (Compt. rend., 154, 447),Rouquette states t h a t sodium hypochlorite was successfully employed for the sterilization of water during a recent cholera epidemic. Water containing 15,000 B . colz per liter was rendered sterile by the addition of I mg. of active chlorine per liter containing I mg. of organic matter. Rouquette states that the best form in which to use active chlorinc for this purpose is as a mixture of &e part of the salt Xa,S,O, (obtained by mixing hydrogen dioxide and sodium hydrogen sulphate in concentrated solution) and two parts of the compound Na,O,Cl (prepared by the addition of sodium sulphate to calcium hypochlorite solution, the calcium sulphate being removed by filtration). The mixture is added in the proportion of 0.oz-o.1 part per IOO,OOO, according to the degree of bacterial contamination. It is said to be more rapid and intense in action than sodium hypochlorite, and the water thus treated is reported t o be odorless and tasteless, and to contain no chlorine, hydrochloric acid or sulphuric acid. PORTLAND CEMENT. A review of the contributions of E. Leduc to the constitution and formation of Portland cement is contained in a recent number of (Naturp, 89, No. 2216, 177), and many useful data, with few speculations, are given. Concerning commercial cements, the fact recognized in practice, t h a t the mechanical strength falls off rapidly as the content of clay is increased, is confirmed in Leduc’s “Sur la Constitution e t la Formation du ciment Portland,” and i t is also shown t h a t the coarseness of grain of both clayey matter and of sand has a t least as great a n influence on the “falling” of clinker as has the amount of their constituents. A normal clinkering temperaturc is set down a t 1 4 0 0 - 1 4 5 o ~ C . Leduc shows t h a t cements in which the alumina is replaced by ferric oxide are mechanically weak, and found t h a t those containing large amounts of magnesia ( e . g., 2 5 per cent.) went to pieces on exposure to steam. “It should be noted t h a t Leduc took unusual pains to bring his raw materials to a n extremely fine state of division, fully comprehending that in a mass which is almost plastic the occurrence and completion of the reactions concerned
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in the production of definite silicates, aluminates, and the like are.dependent on the intimacy of admixture, as well as on the temperature and the time. Any one who has prepared Portland cement experimentally knows that particles of sand which may be only 0 . 1 mm. in diameter will each produce its small center of ‘falling,’ the dicalcium silicate oozing forth from the site of the grain. . . . , whereas the same raw materials, really finely ground, will not ‘fall’ a t all.” I n collaboration with Chenu, Leduc has shown that Seger cones, useful as they are for a number of purposes, are far from exact as temperature indicators; t h a t they may well be used side by side with materials of the same class which are to be heated in the same way, but that in all cases they must be checked by whatever kind of pyrometer is best adapted for the temperatures to be measured.
BLEACHING POWDER AS A SOAP SUBSTITUTE. According to Scientific American Supplement (No. 1897,304), a German physician, Sacher, recommends the use of bleaching powder as a cleansing agent for the hands of workmen as a preventive agent against metal poisoning. Working men handling metals, such as lead, mercury, antimony, arsenic, bismuth, zinc, chromium, or manganese, either in metallic form or in the form of compounds, are constantly exposed to the danger of poisoning, through imperfectly cleaned hands. Small particles may thus be transmitted to the mouth in eating or using tobacco. To completely remove metallic impurities from the hands is sometimes difficult; soap alone is generally useless, especially since it forms insoluble compounds with most of the metals. Bleaching powder, however, is said by Sacher t o be a n ideal material for the purpose; i t has no injurious effects, when properly used, and acts chemically as well as mechanically. It forms a saponaceous lather and has the further advantage of possessing strong disinfecting properties. __--
WATER-GAUGE GLASSES. All users of steam boilers are familiar with the trouble which is occasionally experienced in connection with the glasses used in water-gauges as the result of the corrosion or wasting of the ends of the glass tubes inside the glands of the fittings. Efforts have been made t o get over the difficulty, and many different kinds of glass have been tried, but only a partial measure of success appears to have attended the experimentation, while the rapidity with which the glass is attacked has increased as steam pressures have become higher. The corrosion is always worse at the steam end of the tube than at the water end, and has often led to accidents. According to Engineering (93, 499), in order to prevent this destruction of the glass, a Berlin concern has recently brought out a method for protecting the ends of the tubes. This is said to be accomplished by providing the tube, on the inside and outside of its ends, with a metal protective coating which yields to the expansion of the glass. This is united to the glass by means of a cement that forms a compact whole, which, it is claimed, can not be dissolved by water. For normal pressures, the glasses are provided with a metal sheath a t the steam end; while for high pressures and for water high in alkalies, the tubes are provided with metal coatings at both ends. PACKING IN STEAM PLANTS. Packing for cylinder heads, steam chests, pipe-flange joints, valve stems, etc., is now regarded as indispensable, and the engineer has quite a large line of packings to select from. ACcording to Power (35, 545), the development of the manufacture of packing has proceeded hand-in-hand with the utilization of steam. Up to 1 8 5 0 , for example, the commonly used material ‘was a composition containing red lead, hemp and oil, made into a putty. About 1860, cloth insertion packing was introduced;
