Modern Gasworks Practice

NAPHTHALENE IN COAL GAS 475 largely be deprived of its solvent properties, owing to the over-cracking of the oils upon which thesc properties depend. Ab-der-Halden 1 has studied the effect of artificial carburation and has reached the following conclusions :— (1) Wh.en a coal gas saturated with naphthalene at a given temperature is artificially carburated. it can be cooled below this temperature without the naphtha-lene solidifying, as it is retained in the form of a gaseous solution by the carbür-ating vapours. (2) The efficiency of the treatment depends on the boiling-point of the carburating agent and not on its Chemical composition, and the best results are obtained with. oils boiling between 80° and 90° C. (3) The cooling-point of the treated gas up to which the naphthalene will not solidify out depends on the quantity of the carburating agent used. (4) The influence of carburating coal gas supersaturated in naphthalene is the more marked the greater the content of the naphthalene in the original gas. Carburetted water gas, however, has suffered in quality as a result of the enor-mous advance in the cost of oil occasioned by the world shortage. To-day it contains seldom more than one-third of the solvente which characterized it in pre-war days, and little assistance in the way of naphthalene troubles must now be expected from it. In fact, the use of oil in. most cases has beert discontinued altogether, with the result that the mixed gas as distributed under such conditions is particularly poor in low-boiling vapours. THE ESTIMATION OF NAPHTHALENE IN COAL GAS Colman and Smith’s method depends upon the fact that naphthalene is removed from the gas when the latter is passed through an aqueous solution of picric acid, the naphthalene being precipitated as naphthalene picrate (C10H8, C6H3N3O7) and. free naphthalene. The apparatus consists of five bottles, the first having a capacity of 4 oz., the second 10 oz., the remaining three being of 2 oz. capacity. The first is charged with. a solution, of citric acid which serves to remove any ammonia in the gas, the second contains 100 c.c. of one-twentieth normal picric acid, the third and fourth 25 c.c. each. of the same solution, while the fifth serves to retain any splashings carried over. The fifth. bottle is connected to the meter inlet. The gas is then passed through the bottles at the rate of 0'5 to 1 cubic foot per hour. until 10 cubic feet have passed. The contents of the 2 oz. bottles are then. transferred to the 10 oz. bottle, and all connecting tubes are washed out with as small a quantity of water as possible. An india-rubber stopper fitted with a glass tube, sealed at the bottom, but having a small hole in the side, is then tightly inserted in the 10 oz. bottle, the hole in the side of the tube being just below the bottom of the stopper. The bottle is then evacuated with the water pump as completely as possible, and the glass tube is drawn up so that the hole is well within the rubber stopper, thus sealing the bottle tightly. The bottle is placed in a hath of warm water, the latter being heated to 2 Chimie et Industrie, Jan., 1920.