T H E J O L - R S . 4 L O F I - Y D C S T R I . l L AiVD E.VGi*YEERI.VG
Tune, 1912
of Prof. \Vm. Ostwald, i t behooves us to “put more brains into the goods” and into a greater variety of goods, if the chemist’s B. P. JAGGARD. hopes are to end in fruition. SAS FRANCISCO. ~~
CONTAMINATION OF LABORATORY SAMPLES BY IRON DERIVED FROM CRUSHING MACHINERY. B y VICTOR LENHER.
The article b>- George A . James on the “Contamination of Laboratory Samples by Iron Derived from Crushing Machinery” in TIzc Chemical Engiitccu, 14, 380, Sept., 1911,calls attention to the too oftcn neglected fact t h a t in the preparation of samples for analysis the crushing or grinding apparatus employed may introduce material in such kind and quantity as v.ould rendcr the analysis worthless. Dr. Hillebrand, in Bull. 422, U. S. Geol. Survey, p. 50, lays stress on this point. Too much emphasis cannot be laid on the choice of grinding apparatus used in the preparation of samples for analysis. Recently a series of samples of quartzite were collected by the writer for analysis. Inasmuch as the quartzite beds, from which the samples were taken, were being valued for the purpose of being used in the manufacture of silica brick, it m-as desirable to obtain a n accurate determination of the content of silica and particularly of iron. Metallic iron introduced from crusher. Per cent.
Sample S o .
I...................... 2. . . . . . . . . . . . . . . . . . . . . . . . 3. . . . . . . . . . . . . . . . . . . . . . . . . 4. . . . . . . . . . . . . . . . . . . . . . . 3.
...
. , ..
6 . .. . . . . . . . . . . . . . . 7 . . . . . . . . . . . . . . . . 8
..................... .............. ..............
11. .
....................
12 . . . . . . . . . . . . . . . . . . . . . . .
.................. 14 . . . . . . . . . . . . . . . . . . . . . . . . . 15 .........................
2.92
2.74 2.i3 2 61 2.82 2 59 1 86 2 16 2 65 2.6i 2.81 1 8i 1 98 2 01 2.62
Iron content of quartzite. Per cent. 0 49 0 49 0 0 0 0 0 0
23 63 2.5
29 55 16 75 12 16 06
0 0 0 0 0 20 0 68 0 11
Thc samples on being brought to the laboratory consisted of chips of the rocks, approximating in size ”/, inch square by inch thick. After bcing broken somewhat smaller by means of a hammer, they were reduced in a Braun crusher to pass a 120-mesh screen. The material in the original beds is of a light pinkish cast, while the powdered material was distinctly gray. Tests by the magnet revealed the presence of metallic iron i n the powdered quartzite, but owing t o the fine state of division of the powder, i t was found to be impossible to satisfactorily remove the iron by mean of the magnet. Trcatment of the powder with dilute sulfuric acid and subsequent analysis of the remaining quartzite is shown in the accompanying table. The variation in the amount of metallic iron abraded from the crusher is, of course, dependent on the length of time of crushing. I t is interesting t o note in connection m-ith the above results
CHEJiISTKY.
471
t h a t a similar set of samples were sent to one of the largest iron laboratories in the northwest, and reports were made showing an apparent iron content of the quartzite t o be from 1 . 4 2 2.97 per cent. iron. I t has been the frequent experience of the writer in the analysis of igneous and metamorphic rocks t o find the sample contaminated by iron from the bucking board, crusher, or such grinder as may have been used in reducing the sample. As a rule this metallic iron can be removed and a t the same time determined by treatment with dilute sulfuric acid and subsequent titration with permanganate. As a matter of fact, the more common material which will materially abrade iron or steel in crushing is not appreciably attacked by dilute sulfuric acid during the few minutes contact that is requisite to dissolve the finely divided iron. On the other hand, the general type of ores and products, which will themselves lose part or all of their iron t o dilute sulfuric, mill not appreciably abrade steel from the types of grinding apparatus on the market. It cannot be too strongly emphasized, however, t h a t the chemist is called upon t o report on the constituents sought for, and XT-hcn the common danger of contamination in the prcparation of his sample presents itself, great care must be exercised to eliminate such errors. USIVERSITPO F V’ISCONSIS, MADISOX.
COMBATING MINERS’ DISEASES. =In arrangement has been made with the Public Health and Marine Hospital Service by which one or more surgeons connected with t h a t service mill carry on jointly for that service and for the Bureau of Mines investigations looking to the improvement of mine conditions. These inquiries and investigations have already shown the prevalence of tuberculosis a n d hookworm as miners’ diseases in a number of diffcrent localities in the United States. It is important t h a t this work should be extended more rapidly, because of the fact t h a t the health conditions, as well as the risk of accidents, may be influenced by conditions susceptible of easy improvcment. Furthermore, the large and continuous influx of foreigners into the mining regions of the United States will bring to a n increasing extent the hookworm and other diseases that abound in mines in parts of certain European countries. Various questions t h a t concern the health of workers in mines, quarries, and metallurgical plants can not be answered finally ,without investigations and inquiries t h a t are national in scope, Among such questions are the most efficient methods of preventing the diseases peculiar to certain industries, the most effective sanitary precautions to be observed in and about coal mines and metal mines, and the relative healthfulness of occupations pertaining to mining and metallurgical industries. The investigations and inquiries t h a t are essential to the gathering of reliable information on these questions can be undertaken by the Bureau of Mines, in connection with its collection of accident statistics, in a prompt and efficient manner and a t minimum expense.
BOOK REVIEWS
t
I
Stiength of Materials. By S. E. SLocr-af A X D E. L. HASCOCK. The subject matter of P a r t I relates to the elastic properties X e w York. Ginn 8z Co. Revised edition. 1911. xxxvi of materials, the evaluation of and relation between the elastic 3 7 2 pp. Price, $3 00. constants, stress distribution in straight and curved beams, The present volume is a rex-ised edition of a previous publiunder different systems of loading and support, columns and struts, shafting, thick and thin cylinders, flat Plates, springs, cation appearing in 1906. I t consists of two parts dealing with hooks, arches of concrete and masonry, foundations and reMechanics of Materials, P a r t I, 2 6 2 pages, and Physical Propertaining walls. A most rigid and satisfactory analysis is applied ties of Materials, Part 11, I I O pages.
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