The composition of rhodamine b chlorogallate

ANALYTICA

THE

COMPOSITION

OF

CHIMICA

RHODAMINE

F. CULICIN* Depurlnrent of C’ceut~ogvapky,

AND

The

(Rcccived

ACTA

4x3

B CHLOROGALLATE

J. I’. RIf.EY

U~riversity,

October 3 1st

Liverpool

(GYed

Uritaitr)

, I gGo)

Rhoclaminc B combines, in strong hydrochloric acid solution (6-8 N), with the chloroacids of a number of metals to yield intcnscly coloured red or violet complcscs. The complexes formed with Ga +3, Au+:s, and Sb+” arc soluble in certain organic solvents, such as benzene and chlorobenzcne, and have been used as a basis for sensitive photometric procedures for the determination of these elements’. Except in the cast of antimony” no attempt seems to have been made to determine their constitutions. We have found that the gallium comples, in the organic phase, is represented by the formula (ICH)G~C~.I (Ii -T; rhodamine B). This confirms the formula (RH)MCLI for the complexes of the (&,I = trivalent metal) suggested by ONISHI ~NIB SANDELL~ trivalent elements. ESPERIXIENTAL

Cacsium gallium sulphate (x0 ~6 Ga+3) dissolved in 5 ml of 6.5 N hydrochloric acid containing x o/o w/v titanous chloride was treated with 0.5 ml of a 0.5% aqueous solution of rhodnmine B. The gallium was quantitatively extracted by shaking with 8 ml of a 25% v/v solution of carbon tctrachlotide in chlorobenzeneJ. After filtration through a glass wool plug, the organic phase was evaporated at go”. The residue, which consisted of rhodamine B chlorogallate, was treated with water and diluted to 25 ml. Rhodamine B liberated by hydrolysis of the complex was determined by measurement of the optical density of the solution at 555 m,u in a I-cm cuvette. Quaclruplicate experiments gave optical densities of 0.403, 0.405, 0.406, 0.406. average 0.405. Blank runs were also carried out omitting the gallium (optical densities 0.007, 0.009, 0.0110, average o.oogj. The procedure was calibrated by evaporating to dryness 8-ml aliquots of a solution of purified rhodamine B (x0.0 m&l) in a I : 3 mixture of chloroform and chlorobenzens; the residues were diluted to 25 ml with water and gave optical densities of 0.466, and 0.467. These results lead to the ratio of 69.7,ug Ga: 472.8,~g C3eH3103NaC1, i.e. I atom Ga = 0.987 mole rhodamine B. Attempts were made to recover rhodamine B directly from the organic phase by extraction with water or dilute sodium hydroxide, but although the organic phase turned colourless, no colour was formed in the aqueous phase. * This work was carried out in partial (London).

fulfillment

of the requirements AnaCChim.

for the degree of Ada,

24 (x96x)

Ph.D.

413-414