ELISHA MlTCHELIv SCIENTIFIC SOCIETY. 29 



is reduced by copper when air is absent and at tempera- 

 tures far below 86° C, in fact at the ordinar}^ atmos- 

 pheric temperatures with the formation of copper sul- 

 phate and cuprous sulphide and the production of sul- 

 phur dioxide. 



Finally. — Apparatus similar to that made use of by 

 Andrews^ with ihe modification of having- three drying- 

 flasks containing- concentrated sulphuric acid instead of 

 one, and a Me3^er absorbtion tube was substituted for a 

 sing-le small flask. These served merely as extra pre- 

 cautions ag-ainst dust and insured an intimate mixing- of 

 the outg-oing- g-ases with permang*anate. Within twelve 

 hours the permang-anate was bleached. Andrews' exper- 

 iment lasted only fifteen minutes. The presence of the 

 sulphur dioxide produced was easily detected by the odor 

 when the apparatus w^as opened, and in the bleached 

 permang-anate solution by barium chloride. Copper sul- 

 phate and cuprous sulphide were formed. 



Concentrated Sulphuric Acid is Acted upon by Cop- 

 per at Zero. — Quantitative experiments were carried out 

 by the author when the concentrated sulphuric acid in 

 which the copper was submerg-ed was practically at 

 zero.^ In stating- the results, however, the author g-ave 

 the temperature as "0°-10° C." The flask containing- 

 the acid was buried in an ice-bath and the temperature 

 of the liquid noted by a thermometer inserted throug-h a 

 rubber stopper. The apparatus was air-tig-ht. A stream 

 of hydrog-en g-as was continued throug-h the epparatus in 

 one experiment for six weeks and in another two months. 

 On two occasions when the ice in the bath had melted in 

 g-oing- over Sunday, the temperature rose to 10° C. The 

 temperature could not possibly have remained that hig-h 

 for over twelve hours, which would have had small in- 

 fluence when the experiments lasted throug-h a number 

 of days. The temperature was reported 0°-10° C, how- 



3 J. Am. Chem. Soc, 18, 251, 

 2 Ibid, 17, 908. 



