July 6, 1900.] 



SCIENCE. 



31 



taining bromin* in the place of chlorin, 

 and also others containing arsenic f in the 

 place of phosphorus. How far compounds 

 of this nature can be extended is only con- 

 jectural, but there is evidence of the exist- 

 ence of something of the kind with iron. 



Of binary compounds with the less nega- 

 tive elements, such as the phosphids and car- 

 bids of iron, little is known. Like iron, 

 nickel and also platinum and iridium form 

 phosphids. Iridium phosphid possesses an 

 economic importance in that it enables the 

 metal to be fused in a furnace. Up to the 

 discovery of this process in 1882 by Dr. 

 Wm. L. Dudley, the native grains of iridos- 

 mium were alone available for tipping gold 

 pens, stylographs, and the like. It was, 

 however, found that when iridium was 

 heated to a high temperature in a crucible, 

 on introducing a piece of white phosphorus, 

 the whole mass immediately melted, and 

 could be cast into plates, afterward to be 

 worked up into desired form. This reminds 

 one of the early method of working plat- 

 inum by alloying it with arsenic and then 

 roasting the arsenic ofif in a muffle. 



There remains a single class of com- 

 pounds to be noticed, the ammonia bases, 

 whose greatest development is found in this 

 group. The first member of this class was 

 the compound now known from its discov- 

 erer as the green salt of Magnus, which was 

 first made in 1828. J Then came the work 

 of G-ros, of Reiset, and of Peyrone. Among 

 the many chemists who have cultivated this 

 field are Cleve, Jorgensen, who has given 

 us most of our knowledge of the rhodium 

 bases ; Gibbs, Palmaer, who has developed 

 the iridium bases, and Joly, who has revised 

 the bases of ruthenium ; while the theory 

 of these bases has been discussed especially 

 by Glaus, Blomstrand, Jorgensen, and "Wer- 

 ner. In connection with these bases appear 



*lUd., Ill, 40 (1890). 



^Ibid., 110, 1336 (1890). 



XAnn. der Phys. (Pogg.), 14, 239 (1828). 



what must, with our present knowledge, be 

 considered anomalies. The greatest devel- 

 opment of these bases is found with plat- 

 inum, where nearly or quite a dozen distinct 

 classes of bases are known, and where we 

 find several groups of isomers, which "Wer- 

 ner seeks to explain as stereo-isomers, while 

 Jorgensen strenuously combats the view. 

 In type, the palladium bases resemble those 

 of platinum, but as far as yet studied are 

 much less well developed. Nickel, on the 

 other hand, forms no true bases, though 

 many ammonia compounds. The cobalt, 

 rhodium, and iridium bases are all formed 

 on the same general types, but by far the 

 greatest development is found in cobalt, 

 which almost rivals platinum in the num- 

 ber of classes ; but few of these are devel- 

 oped with iridium, and fewer still with 

 rhodium. In the ii'on group no bases are 

 formed hj iron, and only two or three am- 

 monia compounds ; ruthenium and osmium 

 form fewer bases as far as yet investigated, 

 than any of the other platinum metals. It 

 it interesting to note, however, that one of 

 these ruthenium bases, discovered by Joly, 

 and which possesses intense tinctorial 

 power, resembles very strongly an organic 

 dye, both on fabrics and as a stain in 

 microscopy. The constitution of the am- 

 monia bases is to-day, as it has been for 

 half a century, one of the greatest problems 

 of inorganic chemistry, and it is apparently 

 no nearer solution. In accordance with the 

 valence theory, it becomes necessary with 

 Jorgensen to assume the existence of chains 

 of at least four NH", groups in a molecule, 

 stable enough to be unaffected by aqua 

 regia and also that these ammonia groups 

 are replaceable by water molecules. We 

 must also assume that while in ordinary 

 salts, as for example chlorids, the chlorin 

 atoms, which are directly united with the 

 metal, are dissociated in aqueous solution, 

 in these bases the chlorin which is directly 

 united with the metal is not dissociated, but 



