MONOGRAPH OF THE EXISTING CEINOIDS. 753 



separates; also that alkalies such as potash or ammonia precipitate the pigment 

 with unchanged color. 



fPtilometra miilleri. An alcoholic solution of the coloring matter of what 

 was probably this species was sent to Doctor MacMunn by Prof. F. J. Bell. It had 

 a deep yellow color, being orange yellow by gaslight. It gave one band in orange 

 and one in green, and strongly absorbed the violet end of the spectrum. A very 

 deep layer transmitted only the red rays and showed a narrow faint band in red. 



As the solution was too dilute for spectroscopic observation it was evaporated 

 in a vacuum. After some days' evaporation it left a fine red residue, which in 

 thinner parts seemed yellow and had a pleasant smell, recalling that of Flustra 

 foliacea. 1 



This residue went over easily into absolute alcohol, forming a fine red solu- 

 tion. A deep layer transmitted red only. A less deep layer gave definite bands, 

 and a still shallower lay#r somewhat different bands. These bands gave the fol- 

 lowing readings: First, X598 to X5S9; second, X581 to X562; and third, in a slightly 

 more diluted solution, from X549 to X520. 



On adding hydrochloric acid the color became more orange, less red, and the 

 spectrum changed to that shown in his third figure ; the bands reading, first X589 

 to 7.580, and second, probably composed of two bands, from about X549 to X523, 

 the darker part about X532 523. 



Ammonia added to an alcoholic solution made the color a darker red and 

 caused slight precipitation. A deep layer transmitted red only, while in a shal- 

 lower layer a broad ill-defined band in green was seen. When to this solution 

 ammonium sulphide was added this band disappeared, but no new ones came into 

 view. When an alcoholic solution was treated with ammonium sulphide the fluid 

 seemed redder, and only general absorption of all rays except the red was seen. 

 In thin layers a faint haze was seen in the green, but no bands. 



On treating an alcoholic solution with acetic acid it became a lighter red, and 

 the spectrum changed so that the bands read : First, from X597 to X581 and shading 

 to X562, and, second, in its darker part from X538 to X521.5, the violet being ab- 

 ruptly absorbed. 



Caustic soda changed the color of an alcoholic solution to a darker red, and 

 on diluting still further the color became rose red. The spectrum was the same as 

 with ammonia. 



Nitric acid produced the same effect as hydrochloric, the color changing to 

 orange, and bands like those in the third spectrum appearing, the dark part of the 

 first band reading from X589 to X579 and having a shading on each side of it, and 

 the second band extending from X549 to X523 with its half toward violet more 

 shaded than that toward red. 



Sulphuric acid also changed the color of an alcoholic solution to orange, and 

 the bands were exactly the same as with nitric acid. 



The acid spectrum could be changed into the alkaline by an excess of caustic 

 soda. 



1 Alcoholic specimens of several species are remarkable for their pleasant odor. Tropiometra pictn, T. 

 tnacroiliscus, and I'tilometra miiUeri and Ft. macronema smell much like ripe purple phims. 



