60 SMITH— CATHODIC PRECIPITATION OF CARBON [January 4, 



and one-half grams of tartaric acid were dissolved in water, neutral- 

 ized one-half with ammonia, then diluted to a liter. Portions of 

 this solution were electrolyzed at a temperature of 60° C. The 

 anode was a platinum spiral suspended in a porous cup. The 

 cathode was the foil to which reference has been made. A current 

 of one ampere and twelve and one-half volts acted for a period of 

 two hours. A black deposit showed itself on the cathode. It burned 

 off in the flame. In another experiment, with conditions like those 

 just mentioned, discarding, however, the cup, there was no deposit 

 on the cathode, but the solution was deep yellow in color. Again, 

 in electrolyzing a portion of the ammonium tartrate without the 

 porous cup, but surrounding the anode with a muslin bag, at the 

 ordinary temperature, with a current of 4 amperes and 6 volts, 

 there was a very considerable deposit, black in color, on the cathode. 

 It burned away, with the exception of a mere iridescence, when 

 held in a flame. In another experiment, fifteen grams of tartaric 

 acid were neutralized with ammonia, diluted to 150 c.c. and elec- 

 tiolyzed at 60° C, for four hours, with a current of 4 amperes 

 and 6 volts. The anode and cathode had both been weighed. The 

 cathode became coated with a grayish black deposit. The anode 

 sustained a loss in weight and only one-third of the cathodic de- 

 posit was carbon, the remainder being platinum, which had come 

 from the anode. 



Upon substituting a solution of citric acid (70 grams to the liter) 

 and electrolyzing at 70° C, for three hours, with a current of one 

 ampere and sixteen volts, a heavy black deposit separated on the 

 cathode. It was not affected by hydrochloric acid. It burned away 

 completely in a Bunsen flame. The electrodes were separated by 

 a porous cup. In other experiments a muslin bag surrounded the 

 anode. This bag had previously been well soaked in caustic soda. 

 The usual black cathodic deposit was obtained. It burned away 

 completely on heating. On digesting this deposit with chromic 

 acid, carbon dioxide was obtained and recognized by its reaction 

 with lime water. 



Another trial is worthy of notice. In it a half normal solution 

 of ammonium citrate, made alkaline with ammonia, was electro- 

 lyzed for a period of five hours with a current of 4 amperes and 

 6 volts. The anode was protected by a muslin bag. The solution 



