CHEMICAL SCIENCE. 215 



pavement is a medallion of Flora, which on first being uncovered had 

 a verdigris-green head-dress and flowers ; but as this was unsatisfactory 

 in chromatic arrangement, an examination was made, and, on scraping 

 away the green surface, a beautiful ruby glass presented itself. An 

 analysis showed that the change from ruby to green was due to the 

 fact that the ruby glass had derived its color from peroxide of copper, 

 and that the tessellcc. had become covered with carbonate of copper from 

 a decomposition of their surfaces. London Athcweum, Aug. 



INFLUENCE OF SUNLIGHT OVER THE ACTION OF THE DRY GASES 



ON ORGANIC COLORS. 



A SERIES of experiments have been recently made by Dr. Wilson, 

 of Edinburgh, on the effect of sunlight in modifying the chemical 

 action of eight different dry gases viz. chlorine, sulphurous acid, 

 sulphuretted hydrogen, carbonic acid, a mixture of sulphurous and 

 carbonic acid, oxygen, hydrogen, and nitrogen on organic coloring 

 matters. All of these gases were found to act more powerfully in 

 changing colors when exposed to sunlight than when left in darkness. 

 The effect was greatest in the case of the bleaching gases, especially 

 chlorine, which may be left for three years in the dark in contact with 

 coloring matter without bleaching occurring, provided moisture is 

 excluded, whereas the same gas, though equally dry, was found to 

 bleach dry coloring matter in six weeks if exposed to sunshine, so 

 that a fortnight of sunshine is more than equal to a year of darkness 

 in determining the decolorizing action of dry chlorine. Jameson's 

 Journal, Oct. 



PURIFICATION AND PROPERTIES OF CHLOROFORM. 



PROFESSOR GREGORY, of Edinburgh, in recent investigations, has 

 found that the chloroform obtained from the best manufacturers is 

 almost always contaminated with chlorinated oils, to the presence of 

 which its disagreeable effects are to be ascribed. It is therefore a 

 matter of some consequence to have delicate tests for the purity of 

 this important substance. Pure and colorless sulphuric acid of 1.84 

 at least, on agitation, is colored yellow or brown, as the oil is more 

 or less impure. Perfectly pure chloroform does not color the acid. 

 Pure chloroform when poured upon the hand or a handkerchief rapidly 

 evaporates, while the less volatile oils remain, and are recognized by 

 their color, which is quite persistent. Dr. Simpson has mentioned 

 that, while using a chloroform which had so constantly produced Ui 

 pleasant effects that he threw it away, the handkerchiefs became quite 

 offensive from the smell left upon them which remained after washing. 

 Another test is the specific gravity, which for the perfectly pure arti- 

 cle is 1.500. Mr. Kemp has also noticed another remarkable test of 

 purity. As soon as the acid is no longer colored by the chloroform, 

 the latter exhibits a strong convexity downwards toward the acid. 

 The process for purification proposed by Mr. Kemp is to agitate with 

 strong, pure sulphuric acid, allowing the liquid to remain in contact. 



