The subject matter of a course of ten lectures on some of the arts connected with organic chemistry - Softcover
Synopsis
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. 1854 Excerpt: ...of moistening the valves of the pump, without which care the result of pumping will be inefficient, the so-called air-pump not being intended to pump air, but a mixture of air and water. These directions having been attended to the barometer gauge is to be carefully regarded. If the vacuum could be rendered perfect (which it cannot), the mercury should stand at the same level in both legs of the barometer gauge. In proportion as such an equality of level is reached, or departed from, so will the instrument be in good or bad order. If the mercury refuse to stand, but rise and fall fitfully with every beat and counterbeat of the piston, then there will be somewhere a leak. When such a leak depends on a natural imperfection of the vacuum-pan, and not on a casualty such as the interposition of a grain of sand, or other foreign body, in either of the ground joints, then its discovery belongs rather to the engineer than the manufacturer; nevertheless, for the guidance of colonists and others, who may chance to have a vacuum-pan, and no engineer, a few remarks may properly be given. To determine the exact ground surface to which the leakage is due, it will generally suffice to apply the ear to each in succession, when generally the hissing sound occasioned by the rushing in of atmospheric air will be sufficiently indicative of the leakage. Occasionally other plans must be had recourse to, the most generally eligible amongst which consists in pouring oil or water externally on the ground joint, and noticing whether it remains there, or whether it be forced inward by reason of atmospheric pressure. Should both these means fail to indicate the locality of the mischief, then each joint must be examined in the following manner; indeed the operation now to be described ...
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