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XXXVI IT. On the Conversion of the solid Ferrocyanide of 

 Potassium into the Sesqui-ferrocyanide. By C. F. Schosn- 

 bein*. 



N a former notice I have shown that a solution of the 

 yellow prussiate of potash in water, placed in contact with 

 an atmosphere of ozone, instantaneously destroys the latter, 

 and is converted into the red sesqui-ferrocyanide. Since that 

 communication was made I have ascertained that even the 

 solid yellow salt very readily absorbs ozone and is changed 

 into the red one. If a crystal of the common prussiate is 

 suspended in a balloon containing an atmosphere strongly 

 charged with ozone, and kept in that state by means of phos- 

 phorus and water, it will soon assume the colour peculiar to 

 the red cyanide, just in the same way as it would do when 

 held in air containing chlorine. The surface of the crystal, 

 after having remained in the ozonized air for about twelve 

 hours, is changed into the red salt, which may be easily se- 

 parated from the yellow nucleus by mechanical means. A 

 crystal of about a cubic inch in bulk appeared after thirty- 

 six hours' suspension in ozonized air covered with a crust of 

 the red cyanide, at least one line thick; and in another 

 case I saw a smaller crystal of the yellow salt entirely con- 

 verted into the red one. I hardly need say that by changing 

 the yellow compound into the sesqui-ferrocyanide, the cohe- 

 sive state of the former undergoes a material alteration. The 

 red crust surrounding the yellow nucleus is rather brittle, 

 and consists of a heap of small crystals of the sesqui-ferro- 

 cyanide. It is worthy of remark, that under the circum- 

 stances mentioned the yellow prussiate becomes moist, and 

 exhibits in that state a very strong alkaline reaction. 



XXXIX. On the Decomposition of the Yellow and Red Ferro- 

 cyanides of Potassium by Solar Light. By C. F. Schcen- 

 bein*. 



A SOLUTION of the yellow prussiate of potash kept in 

 r* - the dark does not change its colour, but when exposed 

 to the action of solar light it becomes of a deeper yellow. To 

 render that change very perceptible, a weak, i. e. nearly co- 

 lourless, solution must be used, in which case the liquid will 

 assume a yellow colour after having been acted upon by strong 

 sunlight only for a few minutes. If the bottle containing the 

 solution be closed and not quite filled with the liquid, an 

 odour of prussic acid is perceptible, and at the same time 



* Communicated by the Author. 

 Q2 



