260 Z. Anal. Chem., Band 285 (1977)

Experimentelles

Zu 50 ml einer bei 25~ an Kochsalz ges~ttigten und die ein- gangs genannten Metallionen enthaltenden L6sung, die mit 2 ml konz. HC1 anges/iuert wird, werden 10 ml einer Mischung von ct-Benzoinoxim und Chloroform zugegeben und alles 2 min geschiittelt. Das c~-Benzoinoxim-Reagens wird durch Aufl6sen von 0,15 g in 100 ml Chloroform hergestellt.

Nach Abtrennung des Chloroformextraktes wird die w/iBrige Phase noch mit 5 ml Reagens nachextrahiert. Die gesammelten Extrakte werden, zur Entfernung eventuell vorhandenen Wassers, mit 2 ml 0,5 N HC1 geschfittelt. An- schlieBend wird der Extrakt rnit Hilfe eines Hochtemperatur- strahlers eingeengt.

Nach Abkiihlung werden je 10 Tropfen konz. HNO3 und konz. H2SO4 zugegeben und die L6sung wird abge- raucht.

Nach dem Abkfihlen wird der Riickstand mit 5 ml einer 1 N NaOH-L6sung gel6st und nach Uberffihrung in einen 50 ml-Kolben mit 2 ml einer 10%igen KSCN-L6sung und 15rot einer 5%igen Zinn(II)-chloridl6sung in konz. HC1 versetzt.

Nach 1 h Stehen werden 0,5 ml einer 7%igen Eisen(II)- ammoniumsulfatl6sung zugetropft und die L6sung mit H2O auf 50 ml aufgeftillt. Nach nochnals 1 h Stehen wird die L6sung in einem Scheidetrichter mit 5 ml Diisopropyl/ither geschfittelt und die Atherphase direkt in 5 cm-Ktivetten bei den Wellenl/ingen 405 bzw. 490 nm gemessen.

Literatur

1. Giirtler, O. : Fresenius Z. Anal. Chem. 284, 206 (1977) 2. Peng, R., Sandell, E. B.: Anal. Chim. Acta 29, 325 (1963)

Z. Anal. Chem. 285, 260 (1977) - �9 by Springer-Verlag 1977

Titrimetric Determination of Organic Derivatives of Dithiocarbonic Acid and Carbon Disulphide by Interhalogens

Ashutosh Srivastava

Department of Chemistry, University of Jabalpur, 171 Bhaldarpura, Jabalpur-482002, India

Received June 3, 1976

Titrimetrische Bestimmung organischer Derivate yon Dithiokohlensiiure und Schwefelkohlenstoff mit Hilfe yon Interhalogenverbindungen

Best. yon Dithiokohlens/iurederivaten, Schwefelkohlenstoff- derivaten mit Interhalogenverbindungen; Volumetrie

Organic derivatives of dithiocarbonic acids are of two types, RO.CS.SH and RS.CO.SH. Interhalogen com- pounds were employed for the quantitative oxidation of various of their derivatives. These compounds were determined in the presence of sodium hydrogen carbonate, when corresponding dixanthogens were the oxidation products:

2RO.CS.SK + IX ~ (ROCS.S-)2 q- K I + K X

where X = C1 or Br or C13.

Experimental

All the derivatives of dithiocarbonic acid were prepared from corresponding Na or K alkoxides by reaction with carbon disulphide. The solid product was washed with ether, re- crystallized by dissolving in acetone and precipitated out by adding ether.

Procedure. A sample containing 0.1-1.0 meq. of sodium or potassium salt of dithiocarbonic acid, was weighed in a 150 ml Erlenmeyer flask and dissolved in 50 ml of water after which 0.5 g of sodium hydrogencarbonate was added together with 100 mg of potassium iodide and 1 ml of 1% starch solution. The contents were shaken to dissolve the solid and titrated with 0.05 N aqueous solutions of IC1, IBr or IC13. The end-point was determined by the appearance of the blue starch-iodine colour. Vigorous shaking of the solution during the course of titration is essential.

The new method was applied to sodium and potas- sium salts of 14 organic derivatives of dithiocarbonic acid in which the alkyl radical was methyl, ethyl, isopropyl, amyl, allyl, cyclohexyl, 2-butyl and octyl, etc. The rapid and convenient method yielded results precise to 0.4 % (average of 10 determinations), which are comparable within 0.3 % with the results based on total sulphur analysis and argentometric determina- tion. Of various substances tested only sulphocyanide ion was found to interfere. Bromine monochloride, cyanogen bromide, and iodine cyanide, which were also tested as reagents, were found to be unsuitable.

The above method was also applied to the determination of carbon disulphide. Here, 0.1-1.0 mMole of carbon disul- phide was converted to xanthate by adding 0.5-2.0 ml of potassium ethoxide and 5 ml of ethanol, swirling for 2 rain, diluting with 25 ml of water and titrating with 1 M acetic acid against phenolphthalein. Afterwards, titration according to the above method was performed.