An IMPROVED HYDROGEN SULFIDE GENERATOR C. W. BENNETT Western Illinois State Teacher's College, Macomb, Illinois
A
STEADY, dependable source of hydrogen sulfide under pressure is a prime requisite for most systems of qualitative analysis. The installation to be described represents the sum of improvements made over a period of years on an apparatus designed by J. H. Ransom of Millikin University.'
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TR*Nsom, H., -An efident hydrogen generator, Trans.Illinois State A d . of Sci., 24, 310-1 (1931).
The principle is the same as that of the Kipp generator. Three large bottles take the place of the three chambers of the Kipp outfit. The gas is generated by means of the action of undiluted commercial bydrochloric acid on lumps of ferrous sulfide which are placed over a two-inch layer of broken pottery chips in the bottom of a 4-1.aspirator bottle. The acid is kept in a reservoir made from another 4-1. aspirator bottle
fastened by means of clamps to a foot-length of gas-pipe which is free to move up and down on a large ring-stand. The reservoir is connected by about two feet of rubber tubing to a 2-1. bottle so that, when the latter is full of acid and the reservoir is slightly higher, the weight of the acid will cause i t to flow into the bottle containing the ferrous sulfide lumps. The height of the reservoir is adjusted so that when a very small amount of gas is liberated, its pressure will he sufficient to force the acid back into the reservoir. Thus the
pressure can be kept practically constant. For general use the outlet on the reservoir bottle should be just above the intake on the generator bottle. (See Figure 1.) The unique feature of Ransom's set-up is the use of bolts to hold the stoppers in place against the gas pressure. The present writer mounts the whole apparatus on a board 24" X 12" X 2". Bolts coming up from this base go through oak pieces over the stoppers which hold the latter firmly in place. The two larger strips are 11" X 4" X 1" while the small one over the generator bottle is 6" X 4" X 1". The main improvement, however, is the use of pipe fittings in the gas outlet. This prevents blow-outs and stoppages which are frequent when rubber and glass tubes are used. The detailed drawing (Figure 2) shows the design of this part. A '/z" teeZ rests on an inverted rubber stopper through which is forced a nipple about 4" long screwed into the tee. Below the stopper the nipple goes through the strip used to bolt the stopper in and then through the generator-bottle stopper where i t is tightly held by a bushing. Pipe fittings are always sized according to the inside diameter of the pipe to be used. The outside of the prescribed tee will be perhaps more than an inch in diameter since its opening must be large enough to hold a pipe the inside diameter of which is I/%". These fittings may be picked up from a junk dealer, the local plumber, or from one of the mail order houses.
A horizontal nipple about 4" long screws into the middle opening of the tee and is connected by a union to the permanent gas line so that the generator may be removed a t will.
The permanent service line consists of another nipple about 4" long screwed into a reducing tee which holds a ll/r" pipe in order to prevent clogging and to allow condensation of moisture. At the bottom is a valve for
draining, although this is rarely necessary. The upper part then runs into the elbow connected to the horizontal line imbedded in the back wall of the hoods. (See
Figure 3.) This line consists of a succession of 3/4U nipples and tees reduced to for the outlets which consist of regular gas-stove cocks bought from a chemical supply house. While they do corrode after some time, these are so convenient that they more than make up for the necessity of occasional replacement. The adjuster on the cock should be screwed off and discarded; thus a reducing outlet is left which is suitable for a variety of sizes of rubber tubing. The class must be cautioned always to use the pressure system. The valve must never be turned on unless the flask containing the material to be saturated is fitted with a one-hole rubber stopper canying a glass
tube and is connected to the opening by a length of rubber tubing. If any of the valves are left open in the atmosphere the pressure is lost, with the result that acid will flow into the generator bottle. As soon as the valve is closed the acid makes so much gas that the bottles are insufficient to hold i t and i t will bubble out through the acid. The outfit described will be adequate for a class of twenty-five for a whole term with very little attention unless the FeCla drain becomes stopped up. This can be prevented by the use of ferrous sulfide sticks or fairly large lumps and by avoiding the use of powdered material.
