M. TECHNOLOGY. 553 



the third; and the yellow in solution can be determined by- 

 methods already given. 



V. Violet. Common aniline -violet, aniline -violet from 

 iodine, madder-violet, alkauet- violet, orchil-violet, logwood- 

 violet, and cochineal-violet are chiefly to be considered. A. 

 Immerse a sample in a solution of chloride of lime. 1. No 

 change of color indicates alkanet. 2. Any change one of the 

 other six. B. Immerse another sample in lemon -juice. 1. 

 The violet becomes brighter by presence of one of the ani- 

 line violets, to be distinguished from each other by dipping 

 a sample in hydrochloric acid diluted with three times its 

 volume of water, when it will become violet-blue, and after 

 washing somewhat redder, if it is common aniline-violet; but 

 blue, greenish, and after washing light lilac or pearl gray, 

 if it is aniline-violet from iodine (Hoffmann, "New Parma, 

 Primula," etc.). 2. The sample becomes red, or even yellow, 

 in the lemon-juice. Test for the other four violets : a. Place 

 a sample, after washing it on removal from a solution of chlo- 

 ride of lime, in a solution of yellow prussiate of potash, where- 

 by a blue coloration (Prussian-blue), formed with the iron 

 mordant in the fabric, employed with madder and cochineal, 

 indicates the presence of one of them; distinguishable from 

 each other by the fact that, if the former, the sample turns 

 nankeen-yellow in the chloride of lime solution, and, if the 

 latter, it is completely decolorized, b. Absence of the pre- 

 ceding blue coloration leaves orchil and logwood to be con- 

 sidered. To distinguish between them, immerse a sample in 

 milk of lime, whereby a change to gray, and final, almost com- 

 plete decoloration, indicates logwood ; and a change to violet- 

 blue, orchil. The preceding can also be classified by their 

 ash : thus if it contains iron, madder and cochineal are indi- 

 cated ; if it is white, orchil and logwood ; while the aniline 

 violets afford no ash of their own. The testing of the ash is 

 indeed very important, since the determination of the mor- 

 dant employed iron, alum, chromium may point directly 

 to the accompanying dye-stuff. 5 (7, XX VII., 1874, 212. 



UNIVERSAL GAS-LAMP FOR LABORATORIES. 



This lamp, as described by Muncke, permits the diminu- 

 tion of the flame to any extent without rendering it liable to 

 strike down, and it can also be made to afford a reducing 



Aa 



