August 26, 1898.] 



SCIENCE, 



235 



much less degree, as, for example, chromic 

 and perhaps uranic oxides. 



I will cite, in the first place, the series of 

 metatungstates, the existence of which has, 

 I believe, been fully established, partly by 

 the researches of other chemists and partly 

 by those made in my own laboratory. 



The first term in the series has the gen- 

 eral formula KO.4WO3; the highest ap- 

 pears to be represented by the formula 11 

 K0.24'W03. These, with the intermediate 

 compounds, form a series of homologous 

 terms, the common difference being E,0.2 

 WO3. 



Molybdenum forms a similar, but, in the 

 present state of our knowledge, not so fully 

 represented series. Moreover, in this case, 

 it seems necessary to assume that certain 

 metamolybdates contain a greater or less 

 number of molecules of water as base, either 

 partly or wholly replacing fixed oxides. In 

 my first paper I have discussed this subject, 

 and may here refer to that paper for neces- 

 sary details. A revision of the composition 

 of the alkaline molybdates is much to be 

 desired, taking specially into account the 

 number of molecules of water retained at 

 high temperatures. 



I may here remark that my views in re- 

 gard to the existence of special classes of 

 metatungstates and metamolybdates have 

 not only not found acceptance with other 

 chemists, but, so far as I know, have never 

 even attracted attention 



2. Two different metatungstates may 

 unite to form a double salt, as, for instance, 



I2WO3.5MO + IOWO3.4MO + 66H,0 

 12W03.5Na,0 + 10WO3.4]Sra,O + 51H,0. 



Such compounds, however, are not nu- 

 merous, and it is possible to explain their 

 structure in other ways. Similar molyb- 

 dates have not been observed, except in 

 cases in which other oxides, as, for instance, 

 platinic oxide, are present. 



3. Metatungstates and metamolybdates 



may react with a great variety of other 

 salts to form complex salts in which a rela- 

 tively very large number of molecules of 

 tungstic or molybdic oxides appear, as com- 

 pared with the number of molecules of the 

 combined salt or oxide. 



4. Metatungstates or metamolybdates 

 may unite with complex salts containing 

 tungstic or molybdic oxides, as, for example, 



10WO3PtO34Na,O + 2 |10WO34Na,O} 

 + 72Hp. 



5. Complex acids in the molecule which 

 is united with the tungstic or molybdic 

 oxide appear not to lose their special char- 

 acters and, in many cases, though not in 

 all, to retain their basicity. Thus in the 

 phospho-tungstate 12W03PO^H, the phos- 

 phoric acid is still ortho-phosphoric acid. 

 Two different oxides, acids or salts may 

 unite with tungstic or molybdic oxide, each 

 retaining it own character. I will cite only 

 the phosphoroso-phospho tungstate. 



24W032P03H3P,0,5K,0 + 13Hp 

 and the arsenoso-phospho-tungstate 

 32WO3.I4AS3O3.3PAIOKP + 28H,0. 



Classes of salts have been described in 

 which ortho-phosphoric, hj^po-phosphorous, 

 phosphorous, pyro-phosphoric, mono-meta- 

 phosphoric and hexa-metaphosphoric mole- 

 cules appear as such. 



The first of the formulas above given may 

 be written 



22W03P,0,2K,O.H,0 -|- I2WO3.2POK3 



+ 16 H,0 



and will represent a quadruple salt if each 



term is to be considered as representing a 



double salt. 



6. In the great majority of cases the 

 number of molecules of water in the meta- 

 salts as well as in their derivatives is extra- 

 ordinarily large, but in the present state of 

 our knowledge we are unable to distinguish 

 with certainty between water of constitution 

 and water of crystallization. 



