330 CONTRIBUTION TO STUDY OF HYDROXVLAMINE. — MACKAY. 



found that when a solution of hydroxylamine of fair concen- 

 tration was put in the ordinary cell of the Arrhenius type with 

 electrodes covered with platinum black, tliat a vigorous reaction 

 set in with evolution of bubbles of gas and a greal deal of 

 ammonia fumes, due probably to the reducing action of the 

 occluded hydrogen. Even with bright electrodes considerable 

 decomposition occurred, the resistiince of a solution in contact 

 with the platinum decreasing from 500 to 200 ohms in 18 hours 



It was thought that it might be possible to use some other 

 metal electroplated on the platinum which would not decompose 

 the solution so much. Accordingly, the following experiment 

 was tried with pieces of the more easily electroplated metals 

 about 18 sq. cia. in area. 



Each piece was placed in a beaker and covered with 20cc. of 

 an approximately N/10 solution of hydroxylamine, and allowed 

 to stand at a temperature of 25'' for 44 hours. Each beaker 

 was then washed into a lOOcc. flask, and duplicates of 25cc. 

 each run out from a burette and titrated with iodine solution in 

 presence of sodium phosphate. Averaging the two results and 

 correcting for end point, it was found that 25cc. of each solution 

 required the following amounts of iodine : 



Original solution 11 . Ice. N/10 I solution. 



Solution with tin plate 11.1 



" " platinum 10.5 



" " silver 10.5 



" '.' nickel plate 9.9 



" " mercury . . . .about 8.0 



" " copper 0.0 



It was thus shown that tin decomposed the solution little or 

 none at all, and that copper decomposed it completely, the other 

 metals arranging themselves in the above order. On these 

 grounds an ordinary cell of the Arrhenius type was tin plated 

 from a solution of tin chloride, ammonium oxalate and oxalic 

 acid at a temperature of 65° according to Classen\ a greyish 

 white coating being obtained. 



1. Quantitative Chemical Analyi*ij! by Electrolysis. 



