Dr Turner's Analysis of Radiated Celestine. 331 
stained of an ochre colour. The water contained sulphuric acid 
and iron, even before any sulphate of strontian was dissolved* 
and an ochre-coloured sediment gradually subsided, which was 
a subsulphate of the peroxide of iron. 
On digesting the calcined celestine in water, no trace of iron 
was discovered. 
The absence of the sulphuret of iron was proved by the ac- 
tion of strong muriatic acid on the calcined and uncalcined mi- 
neral ; for no trace of sulphuretted hydrogen could be detected 
by the acetate of lead, even when the mixture was warmed. 
It follows that the fresh celestine contains a minute portion 
of the protosulphate of iron, the presence of which, though in 
very small quantity, gives a strong tendency to disintegration. 
From the combined action of air and moisture, this salt is first 
dissolved, and afterwards converted into the subsulphate of the 
peroxide, causing the ochre stains, which appear as soon as de- 
composition has commenced. The water now acts by dissolving 
the sulphate of strontian, small portions of which are successive- 
ly removed. What takes place in the laboratory, will of course 
occur in the earth, when favourable circumstances present them- 
selves ; the free access of water must in like manner occasion 
decomposition, with gradual removal of the sulphate of stron- 
tian, til} the structure of the mineral is destroyed, and the ori- 
ginal proportion of its constituents completely inverted. 
E. a. 4.085 grammes of finely powdered fresh celestine 
were calcined for half an hour, with 10 grammes of the sub- 
carbonate of soda, and were found, on cooling, to have fused 
into a grey enamel. The ignited mass was digested in pure 
water, filtered, and thoroughly edulcorated. Muriatic acid was 
added, in slight excess, to the clear alkaline solution, and the 
sulphuric acid precipitated by muriate of baryta. The sulphate 
of baryta, collected, dried and ignited, weighed 4.9775, indicat- 
ing 1.6924 of real sulphuric acid. 
b. The solution from which the sulphate of baryta had been se- 
parated, was freed from baryta by Glauber-salt, and was brought 
carefully to dryness. No silica nor alumina was found, but a 
little oxide of manganese was procured by the addition of an 
alkali. 3 
