OF ARTS AND SCIENCES. 81 



The analyses agree well with the formula 



16 WO3 . 8 AS2O3 . 9 NagO + 55 aq, 

 which requires : 



6844 100.00 



The salt gives off vapors of arsenous oxide even on gentle heating, 

 and the determination of the water cannot be made by the use of sodic 

 tungstate. After many trials, it was found best to mix the salt in a 

 porcelain boat with plumbic oxide and carefully heat in a combustion 

 tube, collecting the water in asbestos drenched with sulphuric acid. 

 This process, suggested by my assistant, Mr. Herman Schmidt, gave 

 good results in this case. A solution of the salt gives white flocky 

 crystalline precipitates with baric, strontic, and calcic chlorides. Mer- 

 curous nitrate gives a pale yellow precipitate, which becomes darker 

 on heating, and finally takes a dirty greenish-white color. Argentic 

 nitrate gives a milk-white jjrecipitate, which remains suspended for a 

 long time. Manganous sulphate gives no precipitate, but the solution 

 becomes yellow, and after standing some time yields beautiful bright 

 yellow tabular crystals. Ammonic and potassic arsenates and ortho- 

 phosphates give white crystalline precipitates, which appear to be 

 respectively arsenoso-arsenio-tungstates and arsenoso-phospho-tung- 

 states. The mother liquor of the 16:8 salt gives on evaporation a 

 few crystals in a thick colorless syrup, which, after a few days, forms 

 a pale yellowish hard gummy mass. This may prove to contain 

 a second arsenoso-tungstate. The best method of preparing the 

 beautiful 16:8 salt in quantity will probably be to mix 12 : 5 or 10 : 4 

 sodic tungstate and arsenous oxide in the precise ratio indicated by the 

 formula of the salt, and, after adding water, to boil until the arsenous 

 oxide is dissolved. 



ARSENOSO-MOLYBDATES. 



Arsenoso-molybdates are formed under the same conditions as 

 arsenoso-tungstates, by boiling solutions of acid niolybdates with an 

 excess of arsenous oxide. In this case also there is always a sort of 



VOL. XXI. (n. 8. XIII.) 6 



