Methods of sampling delivered coal and specifications for the purchase of coal for the government Volume 116-121

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt: ...this direction if the level of the coal is below the axis of the cylinder. After the sample has been mixed, the cylinder is rotated one turn clockwise; the coal in the cylinder is then cut by the pianos of the riffle and half of it is discharged into the receiving tray. The coal remaining is again mixed by revolving the cylinder counterclockwise. By alternately changing the direction of rotation, the coal is alternately mixed and halved until about 10 pounds remain in the cylinder. The tray is then emptied of the discarded coal and the 10-pound sample mixed and halved, and the 5-pound sample caught in the tray is put in a container and becomes the official sample while the 5-pound sample remaining in the cylinder is put in a container and held as the reserve sample. The interior of the machine is easy of access and should be brushed clean after each sample. Generally speaking, the use of mechanical means for sampling coal and preparing samples gives more reliable and satisfactory results than hand labor, as the personal equation is partly eliminated. COLLECTION OF SAMPLES IN THE DISTRICT OF COLUMBIA. Gross samples are collected from deliveries under Government contracts in the District of Columbia in accordance with the method given in the specifications and as set forth in this paper. Instead of the gross sample being reduced to 5 pounds, as is necessary in the case of deliveries elsewhere, the sample, after it is reduced to 125 to 250 pounds, is placed in galvanized-iron buckets, each large enough to hold about 70 pounds of coal and having a close-fitting lid that can be locked. The locked buckets of coal are immediately delivered to the crushing room in the Bureau of Mines building, where the preparation of the sample for the laboratory is continued. THE...