alt ie cae ed 
ON ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 261 
Whenever the sedium sulpho-salt solution was coloured yellow by the 
presence of polysulphides these were oxidised by gentle warming with a 
little hydrogen peroxide. 
A considerable number of experiments were made, using varying pro- 
portions of antimony and tin, from which the following typical results 
have been chosen :— 
; A Sodium {Sodium 
Ex) Anti- | Anti- | rin Tin Sulphide] Hy- | o2 | 2! ime-| Rati 
Bert tre mony: mony | taken: | found: | Solution! drate} “2 jS5 sings soy 
ment} taken: | found: grme. grme. | added: ladded: Ag las hours |Sb: Sn 
gre. ErMe- ec. |grme. | O* 
1} 0:2104 | 0°2084 | 0:2052 | 0:2069 50 1 019 | 35} 18 dy oll 
2 | 0:2104 | 0:2107 | 0:2052 | 0-2070 50 1 0:20 | 35} 17h | 1:1 
3 | 0°1052 | 0:°1067 | 0°1026 | 0:1034 50 1 018 | 35} 18 Maal 
4 | 0°1052 | 0°1050 | 0:1026 | 0:1039 50 1 CUS I i Sl pla i Ei iat be 
5 | 0:0840 | 0:0834 | 0:0968 | 0-0964 50 1 0-19 | 2-8; 19 IL 
6 | 0:0505 | 0°0522 | 0:0513 | 0:0516 50 J 0-717 | 39|. 18 LiL 
7 | 0:0420 | 0:0424 | 0:0484 | 0:0465 50 1 0:20} 2:9) 172 | Lil 
8 | 0°0143 | 0°0143 | 0:0193 | 0:0199 50 1 0:20 | 3:2) 19 ane 
9 | 01680 | 0°1700 | 0:0968 | 0:0978 50 1 O20) eS ie ars, 2 
470 | 071959 | 0:°1953 | 0°1026 | 0°1037 50 1 0:20 | 33) 195 | 2:1 
11 | 0°2145 | 0:2132 | 0:0484 | 0:0515 50 1 0:20 | 28} 18 4:1 
12 | 02024 | 0°:2020 | 0:0513 | 0:0517 50 1 O19) | 2:7} 1g ae 
13 | 071430 | 0:1440 | 0:0194 | 0:0201 50 1 0:21 | 3:2) 18 (e5! 
14 | 02045 | 02049 | 0:0020 | 0:0025 50 1 019 | 31) 183 }10:1 
15 | 0°1430 | 0°1459 | 0:0097 | 0:0100 50 1 0°21. | 32) 195 | 1431 
16 | 0°1024 | 0:1023 | 0°2052 | 0°2082 50 1 0°18) 3:0) 193 | 1:2 
17 | 0:0715 | 0:0730 | 0:°1986 | 0°1920 50 1 0719 | 2°6| 20 2 
18 | 0:0354 | 0:0450 | 0:1936 | Not de- 50 1 0-21 | 28} 173 | 1:6 
19 | 0:0354 | 0:0430 | 0°1936 |termined; 50 1 0719 | 2°8) 172 | 1:6 
Other experiments, the details of which need not be recorded, showed 
that :— 
1. The addition of 30 c.c. of the sodium sulphide solution instead of 
50 c.c. for 0-2 gramme of the mixed metals is sufficient, but that there is 
no disadvantage in employing a larger excess of the reagent ; it is there- 
fore better to do so as a safeguard against the deposition of tin. 
2. The addition of sodium hydrate can be dispensed with if 50 c.c. 
of sodium sulphide solution are used. 
3. The electrolysis of the warm sodium sulpho-salt solution of the 
metals with a C.D.,o) of 1:0 ampere gives low results for the antimony ; 
it is therefore preferable to employ the method described, and to conduct 
the electrolysis overnight. 
4. The current must not exceed C.D., 9) of 0:2 ampere, otherwise 
traces of tin are deposited with the antimony. With a C.D.jo) of 
0-3 ampere, the antimony was 6 per cent. too high from this cause. 
Summary. 
The accuracy of the method adopted for the separation of anti- 
mony from tin by electrolysis compares very favourably with that ob- 
tainable by other methods for the separation of the two metals, pro- 
vided the proportion of tin to antimony is not greater than 1 to 1 
«Nos. 1-8). With a larger proportion of tin (Nos. 16 and 17) the results 
