142 



negiitive olectrcuk' coiniilctr rcductinii occurred in ahmit niic-tlilrd tlu» time. 



Ill order further to compare the activity of nas^cent hydrogen made in 

 contact with different metals pieces of sheet coiii)er, tin and i)latinuiu as 

 nearly eqnal in exposed area as possil)le were each made the negative elec- 

 troile from a battery giving practically the same cnrrent. The cell con- 

 tained the same quantity, in solution, of acidified dichromate. The hydro- 

 gen in all cases reduced the solution in about the same time. 



Finally a glass tube about five feet long and one centimeter bore, sealed 

 at one end, was filled witli a good grade of granulated zinc whose surface 

 liad been cleanetl by washing, in turn, with acid, water, amnioninm hydrox- 

 ide and large quantities of distilled water. A solution of chromic acid 

 was made by dissolving a small quantity of chromium trioxide in water 

 which had been purified by re-distil-ing ordinary distilled water from alka- 

 line permanganate and using only the middle fraction which was again 

 brought to boiling for a few minutes immediately l»efore using. The tube 

 containing the zinc was filled with this solution and then one-half of it 

 replaced by well purifiefl hydrogen free from air. The open end of the 

 tube was connected to a smaller tube leading to a vessel of mercury to 

 prevent the escaiie of hydrogen and to indicate any change in the volume 

 of the lattei". The tube was then placed on a table in a horizontal position 

 so that one-half of the zinc was in the li(Hii<l and one-half in contact with 

 the hydrogen. The tube remained in this position from January ninth to 

 ()ct(>b(>r seventeenth last. Except for two months during the summer the 

 lube was observed daily. Xo change in pressure occurred excei»t that due 

 to changes of temperature, and ii(> amount of hydrogen was evt)lved. The 

 solution ])erhaiis, became slightly lighter in color. On opening the tube the 

 hvdrogen burned (|uiefl.v. A little sniiihuric acid added caused tlu' solutitm 

 to become as dark as at the beginning. A little sediment was found in the 

 tiilK' which looked like zinc (vxide. Acid and zinc added to the solution 

 caused rajiid reduction. 



In connection with the -<aiiie sub.iect some i>reliiiiinary work has been 

 dune on the reduction of jiotassium itermangaiiate. I'uritied hydrogen 

 passed into a dilute aqueous solution of the p<'rinangaiiate decolored the 

 siilution in less than twehc hours I'orniiug a brown deposit. In the pres- 

 ence of ]ilatininii foil the redn(tinn was nnn-e I'apid. sonielinics being com 

 jilete in one hour. If the platininn wei'e ••illowed to remain in coniact with 

 the solution for some Mine (be reduction with Indrogeii seemed to be even 



