668 U . S . BUREAU OF MINES NOTES. [J. F. I.

The prevailing conditions in the Panhandle, Big Lake, and McCamey fields were similar to those reported in Bulletin 23I. The characteristic odor of hydrogen sulphide could be detected almost anywhere in the field; also there was a pronounced dark- ening of white lead paint on houses, of brass valves and fittings, and of silver money. The symptoms caused by this gas---both acute (as unconsciousness) and subacute (as eye and respiratory tract irritation ) - -were identical with those produced by hydro- gen sulphide. With the exception of slight gasoline-vapor intoxication and the possible existence of gas-air atmospheres containing an insufficient amount of oxygen to support life, no indications of other toxic gases were noted. The examination of the gases and gas-air mix~tures were therefore confined to analyses for hydrogen sulphide content. Further details are given in Serial 2776, recently issued by the Bureau of Mines.

RECENT PROGRESS IN SLATE TECHNOLOGY.

By Oliver Bowles.

SINCE 1922, when the Bureau of Mines issued a report cover- ing the slate industry in detail, changes in technology have taken place which have an important bearing on the industry. A study of these changes and their effects on the industry has just been completed by the writer. Though the value of slate for roofing, structural, blackboard, sanitary, and electrical uses is generally recognized, it has many competitors. To meet this constantly increasing competition producers are promoting economies in manufacture and improving processes, thereby lessening costs of production, and are placing on the market products of the highest possible quality, thus creating satisfaction and confidence on the part of the user. This endeavor to place the industry on a better basis, both as regards processes and products, is shown in the recent developments in technology.

Among these developments are more efficient mills for manu- facture of roofing slates, utilizing specially designed saws in cut- ting slates which largely replace hand methods of splitting and trimming, use of power-driven machinery in handling blocks, finished slates, and waste, thereby increasing the output and sav- ing a considerable percentage of slate wasted under old hand

Nov., I926.] U . S . BUREAU OF MINES NOTES. 669

methods. Besides the circular saw, a modified type of gang saw has been developed, and is in successful use in several slate mills. Other labor-saving devices include an air-driven slate splitter, power-driven punching machines, and trimming machines for heavy slates. Various new uses are being developed. A new slate product, struco, consists of slabs lacquered in various colors, which overcomes the objection of sombre color, where natural slate color is not suitable to the architectural pattern. Natural variegated slates of irregular shapes produce attractive rustic effects and are coming into insistent demand. Irregular frag- ments usually discarded are now finding pleasing application in walks, floors, and pavements. Floor tile and sawn shingles are being manufactured, and slate veneered shingles with a composi- tion backing are being tested. Further details are given in Serial 2766 of the Bureau of Mines, recently published.

C O M P O S I T I O N OF T H E LIGHT OILS FROM L O W - T E M P E R A T U R E C A R B O N I Z A T I O N OF U T A H COALS.

By R. L. Brown and R. B. Cooper.

IN aN investigation of the distillation products from low- temperature carbonization of Utah (Mesa Verde bed) coal, the composition of the light oils that remain in the gas distilled from the coal under definitely known conditions was determined. The coal was heated at a maximum temperature of about 725 ° by means of superheated steam. Analysis of the coal (as received) showed 3.4 per cent. moisture, 42.9 per cent. volatile matter, 46.2 per cent. fixed carbon, and 7.5 per cent. ash. The oil recovered amounted to 7 c.c. per kilogram or 1. 7 gallons per ton of coal. It consisted of 8 per cent. isopentane, 2 per cent. n. pentane, 3 ° per cent. amylenes, 8 per cent. hexanes, 19 per cent: hexene, 7 per cent. heptane, 6 per cent. heptene, 4 per cent. olefins, 8. 5 per cent. octenes, 7.5 octanes and above. The amount of acids and bases was very slight, a little pyridine was found. Further details will be found in a paper presented before the American Chemical Society meeting in Philadelphia, to be published in a forthcoming issue of Industrial and Engineering Chemistry. The work was conducted in co6peration with the Carnegie Institute of Technology.