8b PROCEEDINGS OF THE AMERICAN ACADEMY 



6 M0O3 . 3 As^O, . 2 MuO 4- 15 aq. 



0.1727 gr. gave 31.77, 31.62, and 31.73 c;^ As.Ogby titrition with iodine. 

 1.1393 gr. " 0.0898 gr. MiuO^ = 7.33(>^ MnO. 



The formula given requires 31.77'^ AsnO, and 7,59 f^ iNInO. The 

 salt gave off arsenous oxide very freely when heated with sodic tung- 

 state. 



PHOSPHOROSO-TUNGSTATES. 



I have already described the class of phosphoroso-molybdates, and 

 will now consider the i^arallel group of phosphoroso-tungstates. The 

 alkaline salts of this series are readily formed by the action of phos- 

 phorous and chlorhydric acids upon metatungstates of the higher order. 

 They are, as a rule, better defined than the corresponding phospho- 

 roso-molybdates, and are in all probability very numerous. The com- 

 pounds to be described will be sufficient to open the subject for further 

 investigation. The analytical methods employed were the same as 

 in the case of the corresponding molybdenum salts, except that after 

 oxidation of phosphorous to phosphoric acid, tungsten and phosphorus 

 were usually precipitated together by niercurous nitrate and mercuric 

 oxide. 



22 : 4 : G Ammonic Phosphoroso-tungstate. — When the solution of 

 phosphorous and chlorhydric acids formed by the action of water upon 

 phosphoric terchloride is poured upon crystalline 12 :5 ammonic tung- 

 state, the salt packs at once into a dense mass. This is to be well 

 rubbed up in a mortar with a large excess of the acid liquid, and 

 allowed to stand for twenty-four hours. The greater part of the mass 

 then presents large granular colorless crystals. A much smaller pro- 

 jDortion of a white fine-grained salt is formed at the same time, and is 

 easily separated by washing from the heavier crystals of the granular 

 salt. This last may be washed with cold water on the filter pump, 

 and dried on woollen paper. In mass the crystals present a faint but 

 distinct tinge of yellow. The salt is but slightly soluble in cold water, 

 but dissolves in a rather large proportion of boiling water to a yellow 

 liquid. The solution gives no precipitate with cupric sulphate, but 

 the mixed liquid becomes somewhat darker on boiling. With argentic 

 nitrate it gives a turbid solution, which becomes purplish on heating, 

 and finally gives a dark dull-purple precipitate. With niercurous 

 nitrate the solution gives a white light precipitate, which becomes 

 deep yellow on heating, and regains its white color on cooling. In 

 this salt, 



