TBANiiACTIONS OF SECTION B. 729 



practical way to the detection and measurement of minute quantities of fire-damp 

 in the air. This was ultimately effected by supplying the hydrogen from a small 

 steel cylinder containing the gas in a compressed condition. The cylinder can be 

 readily carried in the pocket, and, when necessary, it can be immediately attached 

 to the ordinary safety lamp, and made to furnish the standard hydrogen flame 

 burning at a jet in the lamp. The gas is kindled at the jet by the oil flame, which 

 is then extinguished. The accurate estimation of proportions of fire-damp in air 

 varying from 0'2 to 3 per cent, is rapidly and easily effected by the standard 

 hydrogen flame. Higher percentages are estimated either by reducing the size of 

 the hydrogen flame, or by employing the oil flame diminished in size until it 

 becomes non-luminous. 



The small pocket cylinder is under a pound in weight, and when freshly charged, 

 by being connected with a store cylinder at 120 atmospheres' pressure, it carries a 

 store of gas sufficing for over 200 tests. This combined lighting and testing safety 

 lamp has been found to be thoroughly practical in its nature after lengthened use 

 in several collieries, and it surpasses in convenience all the delicate and accurate 

 mine gas-testing apparatus yet described. The lamp, in a modified form, has been 

 adapted to detecting and measuring petroleum vapour in the air. 



7. On the Gases enclosed in Goal Bust. By Professor P. P. Bedson. 



8. A Note on the Temjoerature and Luminosity of Gases. 

 By Professor A. Smithells. 



9. On Ethyl Butanefetracarhoxylic Acid, and its Berivatives. 

 By Bevan Lean, B.A., B.Sc, Bishop Berkeley Fellow of Owens College. 



When sod -malonic ether is treated with ethylene bromide, the chief product 

 is ethyl trimethylene dicarboxylate (I'l), thus: — 



CH,Br CH,. 



I + 2CHNa: (COO C,H,), = | \c = (COO C,HJ, + CH,(COO C,H,), 



CH^Br CPl/ 



+ 2NaBr. 

 But at the same time a small quantity of an oil of high boiling-point is formed, 

 constituting only about 3 per cent, of the whole, which is ethyl butanetetracarhoxy- 

 late,^ thus: — 



CH.Br CH.-0H:(C0OC„H,), 



I +2CHNa:(C00C,H,),= | " ' +2NaBr. 



CH.Br CH^ - CH : (COO CjH,)^ 



The fact that this interesting substance is produced in such small quantities 

 made its further investigation a matter almost of impossibility. More recently, 

 however, Professor Perkin has found that the substitution of ethylene chloride for 

 the bromide is effectual in greatly increasing the yield of ethyl butanetetracarboxyl- 

 ate. As soon as the new method for the preparation of this substance had been 

 thoroughly worked out, I investigated, at the suggestion of Professor Perkin, some 

 of its derivatives, and I desire to give a brief notice of some of the results at which 

 we have arrived. When treated with sodium ethylate, ethyl butanetetracarboxyl- 

 ate forms a di-sodium compound, which reacts readily with the iodides or chlorides 

 of the alcohol radicals. For example, when acted on by methyl iodide the reaction 

 takes place as follows : — 



CHj - ONa : (COO C.H^), CH^ - CCH3 : (COO C..H. )^ 



I +2CH3Br= I ' " +2NaBr, 



CH, - CNa: (000 C,H,), CH, - CCH3 : (COO C,H,), 



ethyl dimethylbutanetetracarboxylate being formed, 



' Perkin, Journ. C. S., 61, 1. 



/4 



