262 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Mangano-sodic Pyrophospho-Molybdate . 



In another part of this memoir I have described several salts be- 

 longing to the group of pyrophospho-tuugstates. As these were 

 peculiar in their constitution, it became a matter of interest to deter- 

 mine whether the pyrophospho-molybdates had a similar constitution, 

 or, in other words, whether they contained the pyrophosphoric group 

 22 RO3 . 9 P2O7 found in the salts of the tungstic series. 



Molybdic teroxide boiled with sodic pyrophosphate, care being taken 

 to keep the oxide in excess, is dissolved with much facility and in large 

 quantity. The colorless solution may be evaporated to a syrup with- 

 out yielding crystals on standing, and gives no precipitates with salts 

 of potassium or ammonium. The solution, however, gives precipitates 

 with salts of most of the heavier metals. Of these I selected the 

 mangauous compounds for special study, supposing that all the manga- 

 nese would be present as base, and that a comparison could be made 

 between salts of this type and those in which manganese exists in the 

 pyrophosphoric molecule, and which I shall describe further on. 



When a solution of manganous chloride is mixed with one of sodic 

 pyrophospho-molybdate prepared as above, a dull bufF-colored ajipar- 

 ently amorphous precipitate is formed. On standing with an excess 

 of the sodium salt, this was gradually converted into a mass of beauti- 

 ful bright yellow crystals. These were well washed with cold water, 

 and then dissolved in boiling water. The filtered solution gave on 

 cooling a mass of sulphur-yellow crystals, which were again dissolved 

 and recrystallized. The salt was then dried on woollen paper. It 

 was analyzed by Mr. G. W. Patterson. 



1.3289 grams gave 0.1065 gram PAMg, = 5.13% PgOg. 

 1.3289 grams gave 0.2486 gram PoO^Mna r= 9.36% MnO. 

 0.9538 gram gave 0.1819 gram P.OyMua = 9.53% MnO. 

 0.9538 gram gave 0.5934 gram P.O5 + M0O3 = 62.22%. 

 1.0960 grams lost with Wo4Na2 0.2037 gram = 18.56%. 

 0.9445 gram lost with WoiNaj 0.1743 gram = 18.45%. 

 The analyses lead to the formula 



22 M0O3 • 2 P2O5 . 7 MnO . 9 NaaO -t- 57 aq., 

 which requires : 



Calculated. Found. 



^ 62.29 



19.20 



18.45 

 5533 100.00 



I 



