TRANSACTIONS OF SECTION B. 669 



The potassium is perhaps over-corrected for errors in weighing, the number 

 actually found being Ai'T ; but 92 milligrams of pot-assium were required to give 

 22'3.3 CO. of hydrogen when weighed as in the experiments and thrown into water. 

 The sodium was similarly corrected. 



5. On the Estimation of the Halogens and Sulphur in Organic Compounds. 

 By R. T. PLiiiPTOxX, Vh.B. 



The estimation of the halogens and sulphur in organic compounds is often a 

 matter of some difficulty owing to tbe want of a sure and generally applicable 

 method of effecting the decomposition of the latter. Heating with nitric acid in a 

 sealed tube does not always suffice for this purpose, and the lime or soda-lime 

 method, besides decomposing certain substances only with the greatest difficultv, is 

 in many respects inconvenient. 



A very satisfactory method of decomposition is the gradual introduction of tlie 

 substance into a Bunsen or hydrogen flame. Provided that the substance be 

 introduced slowly enough, there is no difficulty in effecting its complete deeom]5o- 

 sition. The products of combustion containing the halogen, partly free and partlv 

 as the acid, or the sulphur as sulphurous and sulphuric acids, are drawn throu,"-!! a 

 suitable absorber containing pure soda, and the estimation completed in the usual 

 way. 



As to the method of bringing the substance to be analysed into the flame: — 

 A'olatile bodies are weighed in a small stoppered tube and dropped into a glass 

 Bunsen burner of suitable shape, the substance gradually evaporating iu the current 

 of gas and air. The evaporation is aided or retarded at pleasure by heating or 

 cooling the Bunsen tube. 



Xon-volatile substances are weighed in a hollow platinum gauze wick which 

 can be raised or lowered inside the burner by means of a rack and pinion, so as 

 to gradually bring it within range of the flame. 



A variety of compounds have been analysed by this method with satisfactory 

 results. 



In the case of sulphur compounds it is preferable to use hydrogen, as the cor- 

 rection for the sulphur present in the coal gas burnt in the experiment is too 

 considerable. 



6. Vacuum Injector Pumps for use in Chemical Laboratories. 

 By T. Fairlet. 



7. Description of a Shortened Self-acting Sprengel Vump. 

 By Dr. W. W. J. Nicol. 



8. On the Derivatives and the Constitution of the Pyrocresols.'^ By Williaji 

 BoiT, Ph.D., F.C.S., and Professor H. Schwarz. 



It is about five years since H. Schwarz announced the disco\ery in coal 

 tar of three new isomerides, which he termed a-, (3-, and y-pyrocresol (Ber. XV. 

 2201). Some months previous to this publication W. Bott had examined a certain 

 bye-product obtained at the chemical works of Me>*TS. Grace, Calvert & Co. in Brad- 

 ford in the manufacture of phenol and cresol, and had, independently of Schwarz, 

 succeeded in isolating from it three new substances and prepared several deri- 

 vatives of them. Schwarz's pyrocresols were soon recognised to be identical 

 with the bodies obtained by W. Bott, and we finally resolved to jointly pursue 

 their further study. Unfortunately we have been unable to take up the work 

 until recently, so that it is far from complete at the present time. 



The mode of preparation of the pure pyrocresols and several derivatives has 



' The comijlete original paper is published in the Journal of the So -let y of 

 Chemical Industry. 



