394* Intelligence and Miscellaneous Articles. 



After this calcination the mass was poured on a metallic plate ; 

 this operation was performed in the open air, and it is requisite to 

 protect the face, for without this precaution the vapour of the osmic 

 acid would act strongly on the skin. 



During calcination with the nitre a certain quantity of osmic acid 

 is lost, hut it was ascertained that the quantity condensed hy using 

 a porcelain retort did not compensate for the inconvenience of the 

 operation. 



The fused mass, which contains the osmiate and iridiate of potash, 

 is treated in a retort with nitric acid, which disengages osmic acid, 

 and this is condensed in a concentrated solution of potash • the re- 

 sidue of the distillation is treated with water, which removes the 

 nitre, and then with hydrochloric acid, which dissolves the oxide of 

 iridium ; by these means osmium is obtained in the state of osmiate 

 of potash, and the iridium as a soluble chloride. 



The author found, that by disengaging oxygen from osmiate of 

 potash, and transferring it to other bodies, this salt was readily con- 

 verted into osmiate of potash, which crystallized in fine octahedrons 

 of a red colour. This salt contains, in point of fact, an acid which 

 is less oxygenated than the osmic acid, for by the action of weak 

 acids it is decomposed into osmic acid and black oxide of osmium. 



M. Fremy usually prepares osmiate of potash by pouring a small 

 quantity of alcohol into a solution of osmiate of potash ; the liquor 

 becomes hot and of a red tint, and deposits a crystalline powder of 

 osmite of potash ; in this operation the osmiate of potash is often 

 totally precipitated from solution. This salt may be washed with 

 alcohol, which does not dissolve it, and may be kept, when dry, for 

 an indefinite period ; and it is used by M. Fremy in preparing all the 

 compounds of osmium. 



When osmite of potash is treated with a cold solution of hydro- 

 chlorate of ammonia, it dissolves at first, and soon decomposes, giving 

 rise to a new yellow salt, which is nearly insoluble in cold water ; 

 and this, when calcined in a current of hydrogen, yields perfectly 

 pure osmium. When this salt is treated with hydrochloric acid, it dis- 

 engages osmic acid, and yields a chloride of osmium, which, under 

 the influence of hydrochlorate of ammonia, forms a precipitate of a 

 minium red colour, and very slightly soluble in water ; this salt may 

 also be used for the preparation of pure osmium. — Journ. de Ph. 

 et de Ch., Mars 1844. 



EXAMINATION OF THE AFRICAN GUANO. 

 BY E. F. TESCHEMACHER, ESQ. 



To Richard Phillips, Esq. 

 Dear Sir, 

 It appears from the various analyses which have been made of South 

 American and African guano, that among the numerous ingredients 

 of which it is composed, it is stated in nearly all of them to contain 

 uric acid combined with ammonia. A parcel of guano, however, which 

 I had recently occasion to examine, brought from the coast of Africa, 



