KORNREIOH-"COLOLrR CHANGES OF C'4T AND XZOIC: DYES" Oct. 1946 _ _ ~~

318

for winch dyeing. This selection is based on (a) good fastness to light and washing in pale shades, and (6) eaHo of development, e.g. only u low concentration of w i d ant1 a low temperature ore required.

ualificutioiia to a large extent run parallel, niost of the loledon dyes of interest being enthrctquinonoid and not indigoid derivatives, i .e. they are derived from Caledon dyes rather than from Durindone dyes. The resulting range of shades iS wide and retisonably adequate, ultliougli u t present it lacks a good greenish- yellow and ct bright greenish-blue. This limits the avail- able range of yellowish-greetu and turquoise-blues, but a wide range of hosiery shades can be obtaiiied, whilst Boledon Brilliant Orange URS provides an excellent baeis for the very popular peach shade.

Althougli rewonably low affinity is not a greet disad- vcmtwe with them very pale shdeH, the afiinity of Soledon Blue PRCS is really too low for this work, and this dye would not have been considered if there had been a better altermtive. Apart from its t e c h n i d defects in this respect, its low atfinity makes the production of blue

Fortunately, these two

shade8 on tho winch tlie least economicd of the whole range. For heavy diir.des t8he me of Rolsdon Blue SHCS is inipracticatile, ant1 for ttiili reason t.he inore highly substantive Soledon Blue 4 tJC8 I i w Ooen included in Table 111, although it.# light-fastnew is somowhat inferior and it requires more acid for development. There, is. however, the alternative of using vttt dyes for t,lw Iieavier ~hctdes of blue. Soledon Blue SRCH is fairly satisfectory for iise in mixtures as it sliadiiig tfyq Iwt for self sht~des consideration might bo given either to t.lie possibility of liyctroextraation between dyeing ail( I drvoloping, or ho tho 1180 of standing baths.

The euthor thtlnks Mr. E, Meriiry for his r:o-opcratiotl in much of the work desrribed, and blr. .I. Arclron for mort. of the practioal tlyoiny carried out in (miiitixion with these inveetigations. IMPERIAL C H N M I C A L ~ N ~ ~ U Y T ~ I I K S Liw

DYEBTUFFS DIVISION DYYHOUSE 1 4 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ : ~

I %I,AUKI.EY MAN(SIIBRTE:I~ 0

COMMUNWATION S

The Colour Changes of Vat and Azoic Dyes by Wet and Dry Heat* . -__

E. KoltNmIaft

SUMMARY kl an earlier paperL the author ahowed that the change of shade of dyeings of vat and uxoic dyes on

maping is due to a t r a i t i o n of the dye particles from the amorphous to the crystalline state. Additional evidence is now produced, and i t is shown that two vat dyes deposited in the fibre simultctneously can combine on soaping to form 8 Cryst&lline system different from that of the respect)ive individual dyes.

The Phenomeiivn under IrivwCigativn- Owing to war- time shortage an unusual combination of vat dyea has been used for the production of certain rose shades, vie. Caledon Red 2cf (I.C.I.) and Celedon Red Violet 2RN (I.C.I.). Rose shades of excellent brilliance and of a bluish tone were obtained, but on soaping the brilliance was lost and a yellowish, dull rose shade resulted. This was inexplicable, because it did not represent the clutnge of shade that would be expected from a s u m of the changes of the individual dyes. Caledon lied 2cf chenges very little, if at all, and Cttledon Bed Violet 2RN beoomes m a r k d y b h m on soaping. Instead of becoming bluer, however, the combination changes in the opposite direction. Thia anomalous behaviour seem to be confined to thiR oom- bination. For insttmce, Cdedon Brilliant Oranges P l t nnd 6R (l.C.I.) and &ledon Hsd L%N (I.C.I.), when coni- bined with Caledon Red Violet 2HN, change on soaping in

lCxjuwimuntndIn order to find the reenon for this anomaly, the two dyea were precipihted from solution, iiidividually and in combinetion, as descrilied in the previous paperl. The precipitates were washed by decanting and then treated with Lissapol LS (1.C.l.) (60 g. per 1.) a t b.p. for 1 hr. The precipitate of the oom- bination s h o w the particles of the individual dyea, but after treatment with Liwapol LS the dye8 soom to have merged and the resulting orystul structure h a JlothUlg in common with those of the individual dyes after tlie treatment. These observations were not conclusive, and an attempt was therefore made to obtain evidence by other meentl. From previous experiments i t was hmwn that crystals obtained from solutions of dyes in solvents iire similar to those obtained by the above trestment with Lieaapol L8. The only common solvent for the two dyes under investigation wee found to be copcentrated sulphurio wid. Ever1 so, Celedon Red 2C: gave only colloidal solutions. Small drops of the solutions of the individual dyes and of the combinntion were put on a microscope slide and allowed to take up moiature from the atmosphere. In this way the dye deposited in microscopic orystals. Bip. 1-3 show the appearance under the microscope of Caledon Red 2C; ( b h i n needles), Caledon Red Violet 2RN (round mwms wtlich seem to be aggregatw of m a l l needles) and the mixture of the two dyes. The o stal structure of the combination differs from that o y t h e individual dyes. The thin needles of the Caledon Red Pcf

the expected direction. "'L!'

0 0 1Ux 1- Crystalh ~bf Calaclon PIG. 2 - 4 2 8 h l b of Cleledcn Red &d ZQ from ii aolutlcii 1 1 1 ooncentratoil sulphnric: nrid.

Violet ZRX from a solution In uunoentratrd lsulphurlc acid.

a .., b e

r .

BIU. Y-L?getala of the i i i ix - turc of Caledon lled P f f and Caledon Ued Violet ZYN froin u aohition in concentrated

sulphurlc acld.

have disappeared and the rmultmg mass is sunilar to that of the Caledon W Violet 2RN, but without showing tho apparent egpgatea of needlea. It is evident that the two dyes combine on crystallisation.

A comparative tmt with Caledon Brilliant 0ra11ge 1H end Caledon Red Violet PRN showed that in this case the particles remain separate throughout.

Diucimiott- The above experiments prove that the abnonnal change of ehade on soaping the cornbinstton- dyeing of Caledon Red 2 6 and Caledon Red Violet 2RN IS due to the formation of a uniform crystal structure. ThiH phenomenon shows that the dye particles have consider able freedom of action independently of the fibre, and the author regards this ua evidence for his suggestion' thst aggregation and orystsllisstion play u more important part in the dyeing prooecrs than has hitherto been assumed. 8 ORTHES GROW

HEATON CRAPEL STOCKPORT

(Receiued on 16th April, 1946)

RI~FURMN(%~ Thls Jour., 184'2, 58, 177. T a t . Monuf., 1046, 71, 83.