2 Thomson, Detection of Arsenic in Beef, 



Dr. T. E. Thorpe, C.B., F.R.S. 

 Professor William Augustus Tilden, D.Sc, F.R.S. 

 Professor Harold Baily Dixon, M.A., F.R.S. 

 Graham Aldous, Esq. 

 John Pattinson, Esq., F.I.C. 



With Mr. T. J. Cheater, of the Government Labora- 

 tory, as Secretary. 



This Committee decided on the electrolytic method as 

 the best, and they devised the ingenious little apparatus 

 which was shown by Professor H. B. Dixon at the 

 meeting at which I read my last paper. It consists of a 

 conical shaped platinum band, perforated with holes, as 

 the kathode suspended by the platinum wire which carries 

 the current through the glass stopper of a small bell jar 

 (open at the bottom). This jar stands inside a porous 

 pot, with a narrow circular platinum band outside the 

 porous pot as the anode ; the glass stopper in this bell 

 jar is provided with a glass tube and stop-cock for intro- 

 ducing the liquid to be tested into the porous pot, and 

 with a tube for carrying the hydrogen with any arsenic 

 which might be present to the heated narrow tube where 

 the arsenic mirror is deposited. The porous pot, sur- 

 rounded by the platinum circular anode, with glass 

 bell inside, being set in a circular open glass vessel con- 

 taining diluted pure sulphuric acid (i of acid to 7 of 

 water), that vessel being again placed in a considerably 

 larger glass vessel containing water to moderate the heat 

 caused by the cell resistance to the electrical current. 



At my request Professor Dixon kindly lent me his 

 -electrolytic apparatus, and I have made a somewhat 

 exhaustive series of tests with it in comparison with those 

 ■obtained from the Marsh-Berzelius apparatus when using 

 arsenic-free reagents, and with other forms of electrolytic 

 appliances. 



