Compound Ascidian Diazona violacea, Savigny. 233 



which an Ascidian colony had been wrapped during preservation was found 

 after drying and exposure to air and light to be dyed with a pale pink, not 

 very fast, colour. Qualitative examination showed the presence of a halogen, 

 apparently bromine, for after treating a few milligrammes of the dyestuff by 

 the Carius method a pale yellow silver precipitate was obtained which did 

 not appreciably darken in sunlight and which was slowly soluble in excess of 

 ammonia.. 



The general behaviour of the colouring matter was thus seen to resemble 

 a dibromindigo, which has been shown by Friedlander to be the dye in the 

 case of the Mediterranean Murex branclaris. The chief point of difference 

 appeared to be the bluer shade of tint in all the solvents employed, the 

 greater solubility in ethyl benzoate or acetylene tetrachloride, and except in 

 strong, hot solutions the displacement of the maximum of the absorption band 

 somewhat towards the red. 



As living specimens of Murex brandaris in quantity were not available, for 

 the sake of comparison, the pigment from the closely related British Mollusc 

 Purpura lapillus was therefore examined. 



The purple pigment of this mollusc has already been studied by many 

 chemists.* 



In the present instance the colouring matter from material collected at 

 Port Erin, Isle of Man, was extracted in exactly the same way as described 

 by Friedlander for Murex brandaris, and was obtained in a pure crystalline 

 condition from solution in ethyl benzoate. or acetylene tetrachloride. 



It will suffice here to say chat its appearance and reactions agreed in every 

 particular with the dye from Murex brasndaris : — 66' dibromindigo. Solutions 

 in various solvents were more red purple than those from Diazona, and its 

 absorption band in hot acetylene tetrachloride gave A. = 584 /x/u,. The other 

 three isomeric symmetrical dibromindigos have recently been described by 

 Friedlander,f and their absorption and behaviour in concentrated sulphuric 

 acid are given for reference from the above mentioned paper. 



Compound. 



A. 



Colour in concentrated sulphuric acid. 





H/i. 





44' dibromindigo 



613 



Blue. 



55' 



621 



Blue. 



66' 



585 



Dull violet brown. 



77' 



606 



Greenish blue (peacock blue) . 



* Bancroft, 'Philosophy of Permanent Colours,' 1803 ; Negri, 'Gaz. Chem. Ital.,' 1875; 

 Schunk, 'Chem. Soc. Trans.,' 1879 and 1880 ; Letellier, 'Conipt. Rend.,' 1889. 

 t 'Ann. Chem.,' vol. 388, p. 23 (1912). 



