3 3 2 Dr. withering 0/2 the 
blue was precipitated. To effect this, half an ounce of the 
alkaly was required. This precipitate weighed 19 ; fo that 
the whole of the Pruffian blue weighed 66. After calcination 
in a crucible it was reduced to 3 1 i, and was then wholly 
attracted by a magnet. 
b . Mild fixed alkaly was now gradually added to the liquors 
after the reparation of the Pruffian blue, and a white powder 
was piecipitated. 1 his powder, when well waffied and dried, 
weighed 46 1. After being expofed to a low red-heat for ten 
minutes, it weighed only 32!. 
G. The edulcorated powder (E) was now perfectly white ; 
was not acted upon either by the vitriolic, nitrous, or marine 
acids, but readily melted into a glafs with foffile fixed alkaly ; 
during the melting an effervefcence took place. 
H. The white powder (F) readily diflblved in diluted vitriolic 
acid, and under a flow evaporation formed cryftals which had 
the appearance and the tafte of allum. 
Thefe cryflals were then reduced to powder, and boiled in 
alcohol. The alcohol was decanted off, but did not appear to 
have diflblved any part of the powder; nor did it afford any 
precipitate upon the addition of mild fixed alkaly. 
CONCLUSIONS. 
From thefe experiments it appears, that the Rowley-rag- 
Tone confifts of iiliceous earth, clay, or earth of allum, and 
calx of iron. From the latter muff be deducted nf for the 
quantity of calciform iron, found by experiment to be con- 
tained in the quantity of phlogifticated alkaly made ufe of, 
and then the proportions in 10.0 parts of the ftone will be 
thefe r 
4 
Pure 
