ON ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 257 
(Nos. 5, 9, 10 and 13), it is quite evident that the method is scibélinblet With 
a current ‘density of 0-3 to 0°5 ampere, either throughout the experiment, 
or increased up to 1:0 ampere towards the completion of the electrolysis, 
as in Nos. 9, 10, the deposition is incomplete, and no advantage is 
gained by warming the solution to 60°-70° C. as in Nos. 1l and 12. The 
deposits obtained were bright and metallic in appearance. 
Series IT. 
Ammonium Oxalate Solution kept just Acid by by Oxalie Acid. 
; E Awmonium Oxalic acid pomneian added 
-igaecam : ey oxalate solution 
Pug. 7 added, c.c. At start | During experiment 
0:2160 0:2160 80 40 | 65 
0:2376 0°2382 80 40 60 
0:1050 0:1048 100 _— 80 
In the above three experiments the solution was kept acid throughout 
the electrolysis by the addition of oxalic acid from time to time ; the first 
addition of acid was necessary after four hours. The results are satisfac- 
tory, but the deposits were somewhat powdery in appearance, and required 
very careful washing. In each case a current of 0°54 ampere was em- 
ployed, and an E.M.F. of 3-5 volts ; the electrolysis was completed after 
9% hours, when the solutions had become alkaline. 
Series IIT. 
Ammonium Oxalate Solution Acidified with Acetic Acid. 
: ; Tin Ammonium Acetic acid | 
Experi- | Tin taken: | p 0,4, [oxalatesolu-) solution C.D io | E.M.F. | Time: 
ment Grme, Ginnie. tion added, |jadded, 50 per| Ampere Volts hours 
; cc, cent. ¢.c. | 
1 0:2268 0:2274 100 25 0:67 32 
2 0:2592 0:2576 100 25 0°68 3:3 ot 
3 0:2052 0°2041 100 25 0°50 3:3 183 
4 0:2052 0:2034 100 25 0°32 3:3 19 
5 0°1539 01548 100 25 0-54 37 183 
6 0:1539 0:1537 100 25 0:32 32 19 
6 0:1026 01021 100 25 0:28 3:0 19 
8 0:1026 01012 100 25 0°51 34 183 
9 0:1026 0:1024 100 25 031 3:4 193 
10 0:0513 00518 100 10 0:30 37 183 
11 0:0205 0:0208 100 10 0°32 36 182 
12 0:01025 | 0:0103 100 10 0°35 3:2 183 
13 0:1026 0:1009 100 10 0°36 37 19 
14 0:1026 0°1025 100 15 0°31 3:2 19 
15 0:1026 071031 100 25 0:34 37 19 
‘The tin solution used was the same as in the previous series of experi- 
ments ; the total contents of the dish were diluted to 175 .c. in each case, 
after the addition of the reagents. 
Experiments 1 and 2 show that the deposition of tin from an ammo- 
nium oxalate solution acidified with acetic acid is fairly complete in from 
nine to ten hours, with a current of 0:7 ampere, but the deposit obtained 
is powdery and difficult to wash without loss. By employing a weaker 
current and allowing the electrolysis to proceed overnight, the deposit 
obtained is far better ; 3 itis dark in colour, but adheres “perfectly to the 
s 
