Education of the republic of uzbekistan tashkent state technical university named after islam karimov

RESULTS AND DISCUSSION.
Cobalt (II) from a solution containing H2SO4, thiocyanate 
ions and DMF showed that the optimal conditions for the extraction of cobalt (II) are: 1.25-3.5 
mol / L H
2
SO
4
, 0.5-3.0 mol / L potassium thiocyanate, 13-30 vol.% (By volume) DMF and the 
phases were shaken for 3-5 sec. With equal volumes of aqueous and organic phases, the 
extraction of cobalt (II) with a single extraction is 99.9% and does not change up to a phase 
volume ratio of 40: 1. 
The composition of the extracted cobalt (II) thiocyanate complex was determined by the 
equilibrium shift method [21]. For this, the dependence of the extraction of the distribution 
coefficient of cobalt (II) on the concentration was studied: 1) H
2
SO
4
(from 0.05-1.5 mol / l) at a 
constant concentration of DMFA (20 vol.%) And ionic strength (μ = 1.3), which was provided 
by adding the required amount of KCNS; 2) thiocyanate ions (from 0.05-0.7 g-ion / l) at a 
constant concentration of H
2
SO
4
(2 mol / l), DMFA (20 vol.%) And ionic strength (μ = 1.3); 3) 
DMFA (2 to 15 vol.%), KCNS (1 mol / L) and ionic strength (μ = 1.3): the concentration of 
cobalt (II) in the extract was determined by the photocalorimetric method with the PAN reagent. 
To do this, 5 ml of a 0.03% chloroform solution of PAN and 2 ml of an acetate buffer solution 
with pH = 4 containing 0.2% sodium nitrite were added to the cobalt (II) extract, shaken for 5-10 
sec and the resulting colored complex cobalt (II) with PAN photometric. 
Fig. 1. Determination of molar ratios of cobalt and hydrogen ions (1), thiocyanate 
ions(2), DMFA(3) by the method of equilibrium shift during extraction with chloroform. С
СО
= 
1,695 • 10
-4
m; A
pr
= 0.53 
The data obtained, shown in Fig. 1, show that in bilogorithmic coordinates 
(where D is the distribution coefficient, C is the concentration) there is a linear relationship with 
the slopes of the straight lines equal to 2.4 and 4, respectively. 
Consequently, cobalt (II) is recovered by chloroform in the form of H
2
[Co(CNS)
4
]; the 
solvation number of H
2
[Co(CNS)
4
] in the extract is 3. The number of water molecules associated 
with H
2
[Co(CNS)
4
] in the extract determined by Fisher's method [22] is 5. Based on the 
experimental data, apparently the cobalt thiocyanate complex (II) is extracted from acidic 
solutions in the presence of DMF with chloroform according to the hydrate-solvation mechanism 
[20]: 

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