Author: William H. Welch

Publisher: Forgotten Books

Published: 2019-02-12

Total Pages: 768

ISBN-13: 9781397321657

Excerpt from The American Journal of Hygiene, 1922, Vol. 2 In our routine procedure the soil was thoroughly broken up be fore being emptied into the sieves. Precautions should be taken not to carry over a little of the soil from one sample to another, and to keep the bottom of the sieve from contact with any dirt. The water used in the funnels was usually heated to a temperature of about 115° F. A funnel, after being set up, was filled within an inch and a half of the rim, so that when the sieve was placed in position there would be no contact between the water and the bottom of the sieve. Water of the same temperature was then poured over the rim of the funnel, until it was practically full and the level of the water almost an inch above the bottom of the sieve. The samples were usually set up in the isolating apparatus some time during the day and left stand ing over night before the examinations were made. One method of drawing off the samples of water for microscopical examination was to attach a second clamp higher on the tube and to allow the water between the two clamps to run Off into a 50 cc. Centrifuge tube (see Fig. A simpler method is to slightly Open the clamp at the bottom of the rubber tube and let the water run out until the centri fuge tube is filled. After centrifugation the supernatant water was drawn Off with a long pipette and the residue spread out on a two-by three-inch slide, for microscopical examination: In some instances, when the soil sample was of saturated clay or very finely divided sand, a considerable amount of sediment would fall into the funnel. This could, if necessary, be reduced in amount by running it through a smaller isolating appartus before microscopical examination. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.