OF ARTS AND SCIENCES. 123 



plays tlie same part as tnngstic or molybdic teroxide, or, in other 

 words, appears to enter the compound as VjO., . O3. 



2. Compounds of vanadic pentoxide, vanadic dioxide, and phos- 

 phoric or arsenic pentoxide, may be formed, possessing properties 

 analogous to those of the compounds of tungstic or molybdic teroxides 

 with pentoxides and dioxides. 



3. The series of oxides P2O3, AsjOs, ShjO,, unite with tungstic and 

 molybdic oxide to form well-defined series of complex acids. In 

 these the ratio of the number of molecules of the oxides of the types 

 E0O.3 and IMO3 is much lower than in the cases of the compounds 

 which contain orthophosphoric or ortho-arsenic acids. 



4. Compounds exist which contain one oxide of the R2O3 (or RO3H3) 

 and one of the type R'qOo united to tungstic or molybdic oxide, the 

 general formula being 



m MO3 . n R2O3 . JO R'A • ^ ^"-20' 



5. Compounds exist which contain acids of the types ROoHg (hypo- 

 phosphorous acid, for instance) and R'20j united to tungstic or molyb- 

 dic oxides, the general formula being 



m MO3 . n RO2H3 . p W^O, . r n\0. 



6. Classes of compounds exist which contain oxides of the types 

 RO2 and R'205 united to tungstic or molybdic oxides, the general for- 

 mula being 



m MO3 . n RO2 . p R'.O. . r R2O, 



where, as in the other general formulas, M represents either tungsten 

 or molybdenum. 



7. Compounds exist which contain pyrophosphoric and metaphos- 

 phoric acids in place of orthophosphoric acid. So far as it is jjossible 

 to judge from the salts analyzed, these contain, or at least may con- 

 tain, phosphoric and tungstic or molybdic oxides in a lower ratio to 

 each other than in the orthophospho-compounds. 



8. Complex acids exist which contain two different modifications of 

 phosphoric acid, as, for instance, metaphosphoric and orthophosphoric 

 acids or oxides. 



9. The salts described by Struve and b}^ Parmenfier establish the 

 existence of a class of complex acids, which contain oxides of the type 

 R2O3, corresponding to chlorides of the type RgClg. The true char- 

 acter of tliese salts is for the first time recognized. 



