68 Intelligence and Miscellaneous Articles, 



ammonio-sulphate of copper for blue, sulphuric tincture of roses for 

 red, and water with a little nitric acid for white. The vessels con- 

 taining these solutions stood on a shelf about 12 feet from the 

 ground, and had free sunshine through the day. In the first place, 

 five test-tubes containing a strong solution of permanganate of pot- 

 ash were placed respectively in the five rays. The order of decom- 

 position was blue, red, white, green, yellow. The two first were 

 nearly colourless on the third day, and on the seventh, when opened 

 and tested, contained no manganese in solution. The white and 

 green were not entirely decomposed till the twenty-second day, and 

 the yellow after eight weeks still contained much permanganic acid. 

 In order to determine what was the effect of free contact with the 

 atmosphere upon actinic decompositions, two tubes containing solu- 

 tion of permanganate, the one sealed, the other open, were fixed in 

 phials of the amnionio-sulphate of copper, and cemented to the necks 

 so as to prevent the escape of ammoniacal fumes. In about eight 

 hours the solution in the sealed tube had become colourless, whilst 

 the other retained a deep red tinge. Peroxide of mercury exposed 

 to blue light in a sealed tube was much blackened in four days, 

 whilst a similar portion in an open tube was not affected. Periodide 

 of mercury (prepared by trituration) in sealed tubes and dry gave 

 the following order of action, — blue, red, white, green, yellow; 

 the action of the two latter rays being hardly perceptible, and pos- 

 sibly due to small portions of blue and red light which had not been 

 absorbed by the solutions. In unsealed vessels the action was rather 

 less rapid. Covered with water, the iodide was not affected by any 

 of the rays. This salt is far more stable than is generally asserted. 

 The sample used in these experiments had been kept for ten years 

 in diffused light without any alteration, and even in the blue ray an 

 exposure of several weeks was required to produce any great effect. 

 Periodide obtained by precipitation seemed rather less stable. 



Iodide of starch, perfectly dry, gave the following order: — 

 blue, red, white, yellow, green. The decomposition under the two 

 latter rays was very slow and imperfect. When moist, the iodide 

 was bleached far more rapidly than when dry ; more rapidly also in 

 open than in closed tubes. Perchloride of mercury was acted on as 

 follows : — blue, red, white, green. The yellow ray caused no per- 

 ceptible formation of protochloride. This substance, under the blue 

 ray, gives false results if not perfectly screened from ammoniacal 

 vapours. Peroxide of mercury gave blue, red (considerable), white, 

 green, yellow (very slight). Alcoholic tincture of the green colouring 

 matter of leaves was decomposed very rapidly, and almost simulta- 

 neously in all the rays; apparent order, white, red, yellow, green, 

 blue. Alcoholic sulphocyanide of iron gave — white, blue, yellow, 

 green, red. To determine whether the actinic decomposition of 

 solutions was in any way influenced by their degree of concentra- 

 tion, seven sealed phials were placed in white light, each containing 

 40 parts by measure of concentrated aqueous solution of perchloride 

 of mercury. To No. 2 had been previously added 20 volumes of 

 distilled water; No. 3, 40 pts. ; No. 4, 80 pts. ; No. 5, 120 pts.; 

 No. 6, 160 pts. ; No, 7, 330 pts. The decomposition was most rapid 

 in No. 6, then Nos. 5 and 4. The statement that the blue ray de- 



