with the Mercury Cathode. 367 



The use of this apparatus, however, was of short duration, 

 as in one experiment after the silver chloride coated anode had 

 been heated 11 hours, in intervals, at temperatures ranging 

 from 300°-565°, the weight changed suddenly, showing a com- 

 plete reduction of the silver chloride to silver. The inner 

 chamber was considered permeable to the gases of the flame 

 and the bath thereafter discarded. 



Heating Crucible. — A simple but yet very satisfactory device 

 for heating the anode was made by setting a porcelain crucible, 

 8 cm wide and 4*8 deep, into a heavy piece of asbestos 6 mm thick 

 and about 30 cm square so that only 3 mm of the crucible pro- 

 jected above the asbestos board. A loose cover of mica, with 

 a slit to the middle — the width of the stem of the anode — and 

 a second piece of mica to cover the slit, allowed the anode to 

 be easily introduced and adjusted to any height. The anode 

 hung from a nickel hook. When hydrogen, or a thermom- 

 eter, was introduced into the crucible, holes were cut in the 

 mica cover. In the early work an iron cover with two or three 

 holes of appropriate size was used. 



The temperature of the crucible was determined by use of a 

 nitrogen thermometer. When this was placed 2"5 cm from the 

 bottom of the crucible and the gas slightly lowered it registered 

 390° (corrected). With the full heat of the Bunsen burner the 

 temperature was 530° (corrected"). When the thermometer 

 was lowered to l*3 cm of the bottom of the crucible the temper- 

 ature, at full heat of the burner, was beyond the reach of the 

 thermometer and was considered to be something over 600°. 

 The temperatures were constant and could easily be duplicated 

 by use of the same burner. It was much hotter near the sides 

 and bottom of the crucible, as shown by the fact that the anode 

 could be placed so that silver chloride on the lower gauze disc 

 would melt while that on the upper disc would not melt. This, 

 however, was no serious objection to the use of the crucible. 



Electric Furnace. — A more satisfactory apparatus for heat- 

 ing the anode was made somewhat similar to that described 

 by Goldbaum,* as follows: Six brass rods wound with asbestos 

 cord soaked in water glass were set with screws into a 15 cm 

 square top and bottom of transite asbestos wood 6 mm thick. The 

 diameter of the circle of brass rods was about 10 cm . Water 

 glass wet asbestos cord was wound around the insulated brass 

 rods in screw-like fashion about 40 times, leaving 7 or 8 mra 

 between the threads. Two strands of 3 mm nicrome ribbon 

 were next wound flat into the space between the dried threads 

 with another water glass wet asbestos cords between the 

 nicrome ribbons, thus completely insulating each ribbon. 

 * Jour. Amer. Chem. Soc, xxxiii, 37. 



