638 REPORT — 1903. 



was soluble in dilute sodium hydroxide, giving a yellow solution which was 

 decomposed by dilute sulphuric acid with evolution of nitrogen and oxides ot 



^'*^Wh"n isonitrosoacetone (CHX'O • CH = NOH) in absolute-ether solution was 

 acted on by nitrogen peroxide at a low temperature and the residue left on evapora- 

 tion of the ether heated with benzene red fumes were evolved and diacetylgly- 

 oxime hyperoxide 



CH.,-CO- C = IsO 



I I 

 CH3C0-C = N0 



was produced as a yellow oil. On treating this with phenylhydrazine the 

 monohydrazone 



CH,; C( = N • NHC„H,) • C = NO 



CH,- CO • C = NO 



was obtained in the form of yellow rhombic plates, melting at 161°-162° C. 

 When the monohydrazone was heated with phenylhydrazine, or when the oil was 

 treated with excess of phenylhydrazine, pale yellow rhombic plates of the 

 dihydrazone 



CH,- C( = N • NH • C,H,)- C = NO 



II 

 CHaCC = N - NH - C,H,)- C = NO 



were formed, which melted at 176° C. 



7 Further Investigation on the Approximate Estimation of Mimtte Quan- 

 tities of Arsenic in Food. Bij William Thomson, F.I. C, F.R.S.E. 



The author finds the use of copper foil for wrapping around the portion of the 

 tube to be heated (in the Marsh-Berzelius test), which modification was recom- 

 mended by the Joint Committee of the Society of Chemical Industry and the 

 Society of Public Analysts, to be disadvantageous, more distinct mirrors being 

 obtained by heating the naked glass tube. 



Although arseniuretted hydrogen is said to be decomposed at a temperature of 

 200° C. the author made experiments by heating the tube through which the gas 

 from the Marsh-Berzelius apparatus was passing to .393° C, but got no trace of 



a mirror. 



The best results were obtained by heating the tube to the highest temperature 

 possible, and cooling the portion of the tube on which it was desired to deposit 

 the mirror with a stream of cold water. This was best accomplished by folding 

 over the thin part of the tube a single fold of tissue-paper to direct accurately the 

 stream of water over the portion of the tube on which it is desired to deposit the 

 arsenic. This point is most readily found by the aid of a long wire, thinner at 

 one end than the other : the drawn-out portion of the tube is slightly conical, the 

 thicker end of the wire is inserted, and at this point the tissue-paper is adjusted. 

 The thinner end of the wire becomes arrested when pushed in about a quarter of 

 •an inch beyond the part at which the thicker end was arrested, so that the mirrors 

 are all deposited on exactly the same internal diameter of tube. By this cooling 

 -process only one mirror is "formed, leaving a brown metallic appearance. When 

 the tube is not thus cooled two or more deposits of arsenic frequently take place, 

 the first having a metallic appearance and the other being black. 



It has been suo-o'ested that this behaviour is due to the presence of a trace of 

 oxygen in the hydrogen ; but it is probable that the black deposit is caused by the 

 excessive amount of heat produced by the combustion of these two gases evapo- 

 rating the brown metallic mirror, which at first forms and again becomes deposited 

 as a black powder further on in the tube. 



