Intelligence and Miscellaneom Articles. 635 



Osmiamates are obtained, either directly by the action of osmic 

 acid on a solution of bases in ammonia, as the salts of potash, zinc, 

 and silver, or by precipitating the potash salt by metallic salts, or 

 by decomposing the silver salt by chlorides. 



MM. Fritzsche and Struve have stated that these salts yield no 

 hydrogen by analysis. In two experiments the potash salt gave by 

 combustion vsrith oxide of copper only 0*072 and 0033 of hydrogen ; 

 whereas 0'34 are required for one equivalent of hydrogen. 



The osmiamates undergo an interesting decomposition by the 

 action of hydrochloric acid. The products vary according to the 

 concentration of the acid. If the potash salt be sprinkled with con- 

 centrated acid, energetic action immediately ensues, accompanied 

 with the disengagement of chlorine and probably of its oxide ; the 

 hydrochloric acid assumes a fine purple tint, and the crystals of 

 osmiamate of potash are covered with a crust of small red crystals of 

 two different kinds ; if the salt employed be powdered, and the action 

 of the hydrochloric acid be long enough continued, all the osmiamate 

 undergoes this change ; the nature of which the authors have not 

 hitherto succeeded in explaining. 



If dilute hydrochloric acid be added to a solution of osmiamate of 

 potash saturated cold, no decomposition occurs at common tempera- 

 tures, the metamorphosis taking place only at a higher temperature. 

 It is then more complicated, the liquor temporarily assumes a red 

 and brown tint, and soon emits a smell of osmic acid, which is 

 abundantly disengaged as soon as the liquor is heated to ebullition. 

 If the solution be evaporated to the crystallizing point, as soon as it 

 ceases to emit osmic acid, a mixture of salts is obtained, among 

 which, as shown by the microscope, are hexagonal green tables, green 

 needles, and another red salt, &c. These salts appear to be decom- 

 posed by water, for they were not obtainable by solution and re- 

 crystallization. — Journ. de Ph. et de Ch., Octobre 1847. 



ON THE PREPARATION AND PROPERTIES OF SOME OSMIA- 

 MATES. BY MM. FRITZSCHE AND STRUVE. 



Osmiamate of Potash. — This salt is best prepared by dissolving 

 golid osmic acid in a concentrated solution of caustic potash, with 

 the addition of ammonia during the agitation of the mixture. The 

 solution becomes of a bright yellow tint, and the osmiamate of potash 

 is deposited in the state of a yellow granular powder. The product 

 of the distillation of osmic liquors may also be directly passed into a 

 solution of potash, containing ammonia and properly cooled; the 

 simultaneous distillation of nitrous vapours must be carefully avoided, 

 as they would decompose the osmiamate of potash. 



In both cases, the mother-water which has deposited osmiamate 

 of potash is to be evaporated with a gentle heat ; carbonate of pot- 

 ash may be used instead of caustic, but not so advantageously ; the 

 osmiamate of potash is to be dissolved in a very small quantity of 

 boiling water ; on cooling the solution yields small crystals of the 

 salt of a lemon-yellow colour ; these crystals are of considerable size 



