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THE JOWRNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
transferred to a spitabJe flask or beaker, some methyl red added and then standard acid until the solution is acid as shown by the appearance of the red color of the indicator. No precautions need be taken against over-running this endpoint as an excess of acid is desired. The solution is then
5
vol. 14,”o.
boiled to expel carbon dioxide and the excess acid titrated with standard alkali after the addition of phenolphthalein. The difference between the total alkali and acid used gives the amount of alkali neutraliEed by the citric acid in the sample.
Determination of Suspended Impurities in Gases’ By Wilfred W. Scott2 COLORADO SCHOOL OF
MINES,GOLDEN, COLORADO
The beam caused by liquid mist alone appears as a uniform pencil or band of light, whereas dust particles produce a YNDALL demonstrated that dust particles are re- sparkling effect or irregular flashes of light. The beam is more sponsible for the visibility of rays of light, such as the intense with the gas in motion. Within certain limits the sunbeam or the beam of the searchlight. He did not intensity of the beam is directly proportional to amount of susmake clear the best conditions enabling one to see the beam pended matter in the gas. produced by minute amounts of suspended matter in purified If the gas is dry the beam is completely removed by passgases, nor did he show that a gas free of dust may still pro- ing the gas through a 3-in. mat of loosely carded purified asduce a beam in presence of liquid mist. The opinion com- bestos. If the gas, thus purified of solid matter, is passed monly current regarding the conditions necessary to see the through a liquid the beam again becomes apparent. From beam produced by light rays in purified gas, is that the rays this it is evident that the test must be applied to dry gas if it should be parallel and should be viewed with the visual axis at is desired to ascertain the presence of solid matter in suspenright angles to this beam. Observing these conditions the sion. author failed to see the beam when using direct sunlight, but Fig. 2 shows the apparatus set up for ascertaining the effecdiscovered that a cone of light from an arc light gave a dis- tiveness of a scrubber in a quantitative determination of the tinct beam. This led to the discovery that the beam is solid and liquid suspended matter in a gas. The apparatus best viewed by glancing towards the source of light. AC- is so arranged that comparisons may be made of the unfilcordingly the apparatus shown in Figs. 1and l a was designed. tered gas, by means of a bypass with that of the filtered or
BEAMTEST
T
.Gas Exif
a
For the examination of a corrosive gas, it is advisable to have the chamber o€ the camera made of a material not affected by that gas. For example, in examining purified contact gas a lead chamber is recommended. The interior of the chamber is blackened with dull paint that is a poor light reflector. I n the apparatus shown, circular glass disks close the ends of the tubes a, b, and c. The gas examined enters near the eyepiece b and passes out at the opposite large end. The ray of light is directed through a small opening, either circular (diam.1 cm.) or a narrow slit, located at a, and passes through the arm of the tube and out through a glass window at c. The idea is to avoid light reflection in the chamber, as this would cause a glow in the tube and greatly reduce the sensibility of the test. 1 Received March 3, 1922. Published by courtesy of D. ‘Van Nostrand Co., New York, N . Y. f Associate Professor of Chemistry, Colorado School of Mines; Editor of “Standard Methods of Chemical Analysis.”
C
purified gas. Advantage is taken of the difference in pressures at A and B, so that a continuous sample may be taken of the gas without the necessity of an aspirator. A hand arc light shown on the left furnishes the rays of light which enter at a and pass out into the air at e. The beam is viewed through the eyepiece b. The meter measures the volume of gas aspirated. DETERMINATION OF SOLIDAND LIQUIDIMPURITIES Solid or liquid impurities suspended in a gas may be removed quantitatively by passing the gas through a filter of loosely carded dry asbestos. A filter 2 in. thick and 1.25 in. in diameter is effective in removing suspended matter completely with gas passing through it at the rate of 2 to 3 1. per sec. (5 to 7 cu. ft. per min.). It is essential that the asbestos be free from condensed moisture as a soggy filter is not effective for gas filtration.
