262 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Tke Purple Dye of the Ancients. — In an address delivered 

 at Frankfort a. M., P. Friedlaender has given an interesting 

 account of the highly prized purple dye of the ancients, together 

 with a solution of the mystery of its chemical nature. It appears 

 that Greek and Roman literature supplies abundant information 

 concerning the history of this dye, but the technical details of the 

 lost art of applying it are almost wholly lacking. It is hardly 

 possible that the process was a secret one, since it was employed 

 by nearly all Mediterranean peoples in many localities, hence the 

 lack of information seems to be due to the low social status of the 

 dyers of ancient times. The species of mollusks employed in the 

 preparation of this royal purple are well known, both from 

 ancient descriptions and the remains of broken shells still existing 

 in heaps at places where the dye w T as prepared, and it appears 

 that the sea-snails or periwinkles now known as murex brandaris, 

 mxirex trunculus, and purpura haemostoma were those chiefly 

 used. It is known also that only a very small organ of the snail 

 was utilized. From ancient statements concerning the value of 

 the dyed material the calculation is made that the value of the 

 dyestuff must have been something like $5,000 per pound. 



Several previous investigators have attempted the study of this 

 coloring matter, but without definite results, except that color 

 tests seemed to indicate some analogy to indigo-blue or indigo- 

 red. In undertaking a new study of the matter Friedlaender 

 obtained a supply of mollusks from various Mediterranean 

 zoological stations. After breaking the shells, the glands, which 

 show no color in their original condition, were taken out, their 

 contents were spread upon filter paper and exposed to sunlight 

 for the development of the color. This material was then treated 

 with hot dilute sulphuric acid in order to remove more soluble 

 matters, and then the coloring matter was extracted with a high- 

 boiling solvent, such as quinoline or benzoic ether, from which it 

 was easily obtained pure by crystallization. The yield was very 

 small, amounting to only 1*5 g. from 12,000 specimens of murex 

 brandaris. 



Upon analysis the remarkable fact was found that it contained 

 much bromine, and it was established without doubt that the 

 substance was 6,6, diabrom indigo, a compound already known 

 which can be synthesized in several ways, and which could be 

 manufactured at a price a thousand times less than its cost in 

 times of antiquity. But it is hardly to be expected that it will 

 be used at the present time, for it has a rather dull, reddish-violet 

 color, which makes no marked impression upon modern eyes, and 

 besides the tint can be reproduced by several thio-indigo deriva- 

 tions. Friedlaender says that we have thus lost one of our 



