suined to be 500, 630, 370 aiid 650 mfi, respectively. A n other possibility was considered with reference t o their CoCNS+ complex : the solutions used in their experiments were 0.06 M , while ours have been not more than 0.002 d l . I t therefore seemed possible that a relatively unstablc CoCNS+ complex would not have appeared in our exDeriinents with dilute solutions, but might be revealed a t the high concentrations. Experiments carried out by the method of continuous variations a t a concentration of 0.04 JI have shown this t o be the case (Fig. 7 ) , evidence for the CoCKS+ complex being found a t wave lengths below 550 mp. With absorption in this region, the complex of course does not contribute to the blue color shown by the other thiocyanate complexes. This would be in agrecment with the expectation that such a complex should he hexacoordinate and of the "red" type, rather than trtr'ccodrdinate "blue" type2as is the tetrathiocyanate coniple\ I t should be pointed out that the complex probably 5houIrl be written Co(CSS)(ClO*).S solvent, since cobalt perchlorate is only partially dissociated in acetone.' I t seems hardly necessary to emphasize here. nh,ct I, true for the several cobalt salts investigated, and probabl., also is true for many complexes of other metals: whcti *in analytical method depends on ma5muni comple\ for-
I C O \ I K I I 1 1 l I O \ PKOhZ i l I F C I I k 1 I I \ l K \
mation, ketone incdiurn (as contrasted with aqueouh or alcoholic) may he expected to give greatest sensitivity. _. I his is e5pecially true for colorimetric procedures in which the cstinction coefficients of the highest complex are greater than those of other complescs which may he formed.
Summary 1. In very dilute solution in acetone, cobalt(I1) yields trithiocyanate and tetrathiocyanate coinplexes. 2 . In dilute solution in isopropyl or t-butyl alcohol, only dithiocpanate and trithiocyanate complexes are found. :I. The extinction coefficient of the tetrathiomate complex is :tboiit twice that of the trithiocy-mate complex. 4. I n relatively concentrated solution in acctoric, a n unstable complex involving a single thiocyanate group can he identified. 80,
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it10
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This inethocl hds also been used to determine the equilibrium constants of some Lirconium coni$exes. The present work wa5 undertaken to detertniric the stability oi complex ions formed betweeri thorium and the anions of several monobasic acids. The acids studied were hydrochloric, nitric, chloric, bromic, hydrofluoric. chloroace tic., tlichloroacetic, trichloroacetic, acetic. and furinic. The TTA extraction method wa5 used throughout (1) The work covered in tliii payer i b r l , Lrirird out U I I C ~ ~i l Ir r .~uspicesof the 4tomic Energy Comrnhiuit i t O a k Ridgr \ s t i i , r i r I I,.iburatory.
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