IODINE. 157 



pors of iodine from the mixture. These being led into 

 a receiver, crystallize in brilliant scales. A retort and 

 receiver are commonly used in the process. The ashes 

 of sea- weed, employed for the purpose, are called kelp, 

 and are prepared in great quantities on the coast of 

 Scotland. 



VIOLET VAPORS or IODINE. 



violetlapors Introduce a few scales of iodine into 

 of iodine pro- a test-tube or vial, and heat it for 



duced? 



a moment over the spirit lamp. The 

 solid iodine is immediately converted into a 

 beautiful violet vapor, which fills the vial. As 

 the latter cools, the iodine becomes again solid, 

 in the form of minute crystals. On warming 

 these crystals, thejeolbr re-appears. 



^^077. COLORING EFFECT ON STARCH. - 



Describe the jj eat a |j u i e i O( J me i n a ^ive 

 effect produ- 

 ced by iodine stem, and as soon as vapors ap- 



paste? C pear, blow them against a sheet 



of paper, covered with figures 

 made with thin starch paste. The iodine vapor imme- 

 diately colors them blue. The paste may be made in 

 a test-tube, over a spirit lamp. 



378. ENGRAVINGS COPIED BY IODINE.- 



How are en- 

 gravings copi- A transient copy of an engraving, or other 

 ed by iodine ? p rm t ec j ma tter, may be made, by exposing 

 it to faint fumes of iodine, and then pressing it down 

 upon paper moistened with vinegar, or dilute nitric 

 acid. The vapors, adhere to the ink only, and are 

 transferred by pressure ; producing, with the starch 

 contained in ordinary letter paper, a blue impression. 



