1546
JOURNAL 01.
CHEMICAL EDUCATION
DECEMBER, 1927
A NEW AUTOMATIC HYDROGEN SULFIDE GENERATOR H. H. BARBER,UNIVERSITY OP MINNESOTA, MINNEAPOLIS, MINNESOTA
The preparation of large amounts of hydrogen sulfide by the action of an acid on ferrous sulfide has presented to a number of schools a problem which has not been satisfactorily solved. The Kipp generator is satisfactory when the number of students is small, but as soon as the number becomes large, requiring several Kipp's or individual generators, dissatisfaction with this method of obtaining hydrogen sulfide has been felt. The glass Kipp is easily broken. It is not easily filled or cleaned, and as it has only one outlet, unless attached to a pipe with several outlets, the use is very limited. To overcome these difficulties, various types of generators have been proposed, and have more .or less satisfactorily replaced the Kipp for the preparation of hydrogen sulfide on a large scale. Most of these generators, however, have serious defects. Some are hard io fill and hard to clean. Others feed the acid onto the ferrous sulfide a t the top of the column. This type of generator soon ceases to generate hydrogen sulfide as the fine ferrous sulfide and insoluble material are carried toward the bottom of the column and form a mass which stops further flow of the acid over the ferrous sulfide. This mass then forms a hard cake that must be removed, usually with difficulty, before the generator can be used again. The generators with attached storage tanks require considerable space, are =pensive, and are not easily handled. Defects in construction, trouble in handling, and back pressure of the gas often cause the hydrogen sulfide to escape into the generator-room with attendant dangerous, disagreeable, and ill effects. Recognizing the need of a better hydrogen sulfide generator for large classes, experiments were carried out on various types of generators. Numerous arrangements were tried, and experiments were conducted with several new designs. The generator described in this article is the one that gave the best experimental results. A battery of three has been in use for some time and has been found to be entirely satisfactory. The generator is constructed of acid-resisting earthenware and consists essentially of five parts, which, for convenience of description, are designated A , B, C, D, E (Fig. 1). The flanges of parts A , B, and D have flat ground surfaces. The assembled generator is shown in Fig. 2. The generator is set on a flat place which is bulk on a slightly slanting cement floor with a raised gutter arrangement a t the lower edge of the slant. The gutter leads to a sewer-connected outlet. Behind the generator a t a height of 18 inches, a shelf is placed on which the acid container rests. The whole arrangement is enclosed in a room provided with an outlet ventilating
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fan. To this room iron pipes are run for leading the hydrogen sulfide to the various laboratories. This room is also provided with an outlet for cold water. In order to render the generator gas-tight, the parts are held in place by two iron rods inch in diameter. These rods are set in the cement floor. They are 18 inches apart and have a length of 39 inches from the surface of the floor The rods are threaded for 3 inches a t the top. An oak clamp, 22'' x 7" x 2", with a 2-inch hole a t the center and a inch hole in the middle of the clamp, 2 inches from each end, is provided. The manner of using the rods and clamp is shown in Fig. 2. The generator is set up by placing section A between the iron rods. The upper opening is connected to the acid container by pure gum rubber tubing. The lower opening is closed with a rubher stopper. On the ground flange a soft rubber gasket, '/a inch thick, is placed. Section B together with section C in place is now set on section A . Section B is filled with lump ferrous sulfide. (Ferrous sulfide pieces about 2 inches in diameter are suitable. Larger or smaller lumps may be satisfactorily used. No screening for size is necessary, but a large amount of very fine material should be avoided, especially a t the bottom of section B.) Another rubber gasket is placed in position on the upper flange of section B, and then section D is set on. The upper outlet of D is attached to a piece of z/cinch inside diameter pure gum rubber tubing. The tubing is passed through the 2-inch hole in the oak clamp, and then connected to the gas supply lead. The distaoce from the top of the generator to the gas supply connection should be about 18 inches. This gives flexibility in lifting off and on section D. The iron rods are now inserted through the holes a t the ends of the clamp and sections A, B, and C firmly brought together by screwing down the nuts. The other outlet in section D is closed with a rubber stopper. Operation of Generato* Close the valve in the pipe above the generator. Add to the acid container 41/%gallons of water, and then allow 2 quarts of concentrated commercial sulfuric acid to run slowly into the water. Open the valve above the generator. When the stopcocks in the laboratories are opened the flow of the acid will so regulate itself, owing to the construction of the generator and the large surface of ferrous sulfide present, that hydrogen sulfide will not bubble back through the acid container unless a heavy flow of gas is suddenly stopped. After the acid bas become spent, the rubber stopper a t the bottom of section A is removed. The rubber stopper in section D is now removed and through the opening a stream of water is passed until it runs prac-
VOL. 4,
No. 12
NEW AUTOMATIC HYDROGEN SUL~D GENERATOR E
1549
tically clear. By this treatment all of the insoluble material carried into section A, the ferrous sulfate, and silt will be removed and a fresh clean surface of ferrous sulfide will be left in the generator. The a d d container should also be washed. Allow the water to drain from thegenerator; close the openings in sections A and D; fill the acid jar with fresh acid. The generator is now in fine operating condition. If a thorough washing of the ferrous sulfide is carried out after each lot of acid is spent, it will not be necessary to open the generator until the whole of the charge, about 200 lh., of ferrous sulfide has been used up, as the ferrous sulfide will move toward the bottom of section B as it is dissolved, and the acid lead from section E to section A will not become clogged by the insoluble material. One generator of the size described in this article will supply hydrogen sulfide in sufficient quantity for 200 students working in qualitative chemistry when closed precipitation flasks are used. These generators may be obtained from the ceramic companies for about 837.00. The cost of hydrogen sulfide when prepared from commercial ferrous sulfide and sulfuric acidwill be approximately 25'$the pound. Summary A new automatic hydrogen sulfide generator, simple in construction, inexpensive, and positive in operation has been described. The generator is easily filled and cleaned,.and does not clog in operation. The generator is not easily broken, and may be constructed in any size to suit the laboratory requirements. The generator may be easily secured on specifications from the ceramic companies.
Airship Gas Source Seen in Atmosphere. Airship makers rake courage. Helium, the valuable safety gas so much in demand for filling balloons, may be obtainable in unlimited quantities from ordinary air. This optimistic suggestion comes from Dr. Frederick G. Cottrell of the Fixed Nitrogen Laboratory, one of the country's foremost experts in the chemistry of the atmosphere. Unfortunately, there is but one part of helium in 180,000 of common air. On the other hand there is a lot of air. Dr. Cottrell's hopes are based on the prospect of separation of air into its component gases in a large industrial way, whereby the oxygen, in particular, is t o be more efficiently used in combustion. When this sort of wholesale air analysis is undertaken, the helium content of the atmosphere will unquestionably get attention. It is estimated that some fifty million cubic feet of helium per year go through the blast furnaces of America, along with the enormous volume of air feeding the fires. If i t could be salvaged, this quantity of helium alone would revolutionize the airship industry.-Science Service
