624 Foreign and Miscellaneous Intelligence. 



were found to have increased by 7.01, which would correspond to 1 

 atom of the iodide, and 2 atoms of ammonia, equal to 100 parts of 

 the former, and 7.54 of the latter. By exposure to air, ammonia is 

 rapidly evolved, and the red colour of the iodide restored. 



Cyanide of Mercury combines so very slowly with ammonia, 

 that I was unable to continue the experiment for a sufficient length 

 of time. After several days, 0.760 parts of the cyanide had acquired 

 0.060 parts additional weight, which would be 7.90 of ammonia 

 to 100 parts of cyanide. The compound is perfectly soluble in water, 

 and, on being heated, loses its ammonia. 



Some oxides were also submitted to the above method, but without 

 obtaining any results ; the oxides of copper and zinc at least did not 

 seem to combine with ammonia. 



The above experiments seem to me to be of interest, inasmuch as 

 they shew that some anhydrous salts combine with ammonia, whilst 

 others do not, and that in the compounds there exists a definite ratio 

 of the elements. It is further worthy of remark, that in some com- 

 pounds, the salts of which are very similar one to another, the pro- 

 portion of ammonia should be so very different. The compounds 

 which anhydrous salts, and the chlorides, bromides, &c. form with 

 ammonia, appear to me to have some analogy to the combination of 

 these substances with water ; for of those salts, which possess similar 

 properties, some form hydrates, and others do not : in some, the 

 water of crystallization is in a different proportion to what it is in 

 others ; and in all, it is in a definite ratio to the elements of the salt. 

 Lastly, most hydrates emit their water of crystallization very easily ; 

 but in a few it is rather fixed ; this is also the case with the compounds 

 of ammonia and anhydrous salts*. 



12. TEST OF THE PROTOXIDE AND PEROXIDE OF IRON. (Berzelius.) 



To determine the exact quantity of the oxides of iron in a substance 

 which is soluble in acids, Berzelius proposes the following method : 

 A bottle, with muriatic acid, is closed air-tight, after all atmospheric 

 air has been expelled by means of carbonic acid ; the substance 

 which is to be examined is carefully weighed and dissolved in the 

 acid by a gentle heat. What remains insoluble, is washed with boil- 

 ing water (which must be free from air) , and this, as well as the so- 

 lution, is put into a bottle containing a certain quantity of silver in 

 powder and water, which has been freed from its air by boiling. The 

 bottle is now carefully closed, and the liquid digested at a little below 

 212 F., and frequently shaken. After it has become colourless, 

 which sometimes requires about twenty-four hours' digesting, it is 

 filtered, and the metallic powder washed, dried, and weighed; the 

 excess of weight consists of chlorine, 44.26 of which correspond 

 to 97.84 of peroxide in the substance ; the rest, if it had been ascer- 

 tained that the substance contains more iron, consists of protoxidef. 



* From PoggendorflPs Annalen, Bd. xx. St. 1. page 147. 

 f Berzelius, Lebrb. Band 4, S. 757. 



