A NEW HYDROGEN SULPHJ.DE GENERATOR. 521

LV.-A New Hydrogen Sulphide Generator. By BERTRAM DILLON STEELE and HENRY GE.ORGE DENHAM.

THE chief defects common to the usual laboratory forms of hydrogen sulphide generators are to be traced to the comparative slowness of the reaction between acid and sulphide, especially when the concentration of the acid has reached a low value. In con- sequence of this, a very large apparatus is necessary if it is desired to supply each member of a class with a constant supply of gas, and in order to attain this there is, in general, a great wastage of partly spent acid. I n the apparatus herein described, an endeavour has been made to obtain (1) a rapid evolution of gas, and (2) com- plete neutralisation of the acid.

Preliminary experimenh on the effect of temperature on the velocity of the reaction between iron sulphide and hydrochloric acid were carried out in 1911 by Mr. I. Rosenblum a t the sugges-

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528 STEELE AND DENHAM:

tion of one of the authors, and it was soon established that the two desired objects could be readily attained by bringing about the reaction in the neighbourhood of looo. The following apparatus was then designed: ,4 is the acid-holder containing about 15 litres, B a smaller

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reservoir t o retain hydrogen sulphide generated after the tap C is turned off, D a piece of capillary tubing, 3 cm. long and of 1 mm. bore, inserted to prevent a too rapid outrush of acid when the taps are opened, F represents a steam-jacket either of glass or of galvanised iron, iK a wash-bottle, H a reservoir, of 25 litres capacity, to receive the spent acid, and k a tap through which the spent

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A NEW HYDROGEN SULPHIDE GENERATOR. 529

acid may b'e readily removed. As a matter of convenience, it is advisable to have H sufficiently large to hold the maximum amount of acid required per demonstration. I n order to facilitate the displacement of air from the vessel H by the incoming spent liquor, the tube L has a number of holes blown in it. The steam may be supplied from a 500 C.C. flask, G, and experience has shown that with a short air-condenser attached to J there is practically com- plete condensation of the escaping steam, so that little or no atten- tion is required.

Mode of Operatiolz.-The apparatus, F, is packed with lumps of iron sulphide, and the acid-holders are filled with commercial hydro- chloric acid diluted with an equal volume of water. On opening the tap C, acid begins to drip on the sulphide, and. urovided steam has been passed through the jacket for a sufficiently long period t o ensure thorough heating of the sulphide, each incoming drop of acid reacts with almost explosive violence, and long before the acid has percolated through the heated column it is completely neutralised. I n fact, a few pieces of iron sulphide placed in the receiver H were found to be unacted on after the apparatus had been in constant use for seven months. After generation, the gas passes through the tap C and the wash-bottle M before distribu- tion to the students' benches. On turning off eithelr the tap C or the bench taps, the gas generated by the last few drops of acid passes back into the holder B and forces acid into the upper vessel A .

General Remarks.-Hydrochloric acid (1 : 1) has been found to be more suitable than sulphuric acid, owing to the great tendency of ferrous sulphate to crystallise out as the spent liquor passes from the heated generator into the receiver, thereby causing a block.

The apparatus of the dimensions indicated in the figure is sufficiently large to supply hydrogen sulphide to the bench of every student in a class of fifty-four, and will stand all demands made on it when this class is engaged exclusively on the analysis of mix- tures containing a t least four bases from Groups I I A and IIB, even t o the extent of enabling them t o prepare their own ammonium sulphide. As an example of the economy of the apparatus, a series of tests showed that the average consumption of concentrated hydrochloric acid per demonstration of two hours by each student engaged as above in Group I1 analysis amounted to 14 c.c., which was equivalent to 2300 C.C. of hydrogen sulnhide a t normal pressure and the ordinary temperature. THE DEPARTMENT OF CHEMISTRY,

UNIVERSITY OF QUEENSLAND, BRISBANE. [Received, November 24th, 1919.1

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