Factitious Puzzolana . 
2m 
The exeess of aliunen causes the plaisters made from 
the Italian puzzolana to crack and chap in the open air : 
this fault arises from their great oxidation. I have been 
able to replace in them those principles which they lost 
by decomposition. 
Analysis in the dry Way. 
I endeavoured to obtain a regulus from these oxides 
of iron by using a violent heat. I followed the process 
of Kirwan for the fusion of siliceous and argillaceous ores 
of iron ; yet I never obtained a single metallic button ; 
and only found at the bottom of the crucible a vitrified 
mass of an opaque black, or a scoria in the state of crude 
cast iron. 
Desirous to know if I could procure a malleable but- 
ton by using the blowpipe, taking borax for the flux 
and supporting the oxide on charcoal; I still could only 
obtain a spongy ingot resembling crude cast iron, and 
breaking both when hot and when cold. 
Being placed on a support of glass, (according to my 
method published in the Journal de Physique, tome 31, 
pages 116 and 139,) the oxide fused at the second at- 
tempt, the support was coloured green, and small grains 
of iron were seen to pass first of a dark-green colour, then 
of a bright green, and afterwards to disappear in evapo- 
rating. There remained on the globule only a slight 
tinge of blackish- green. 
The result of all these facts seems to be, that this 
oxide is entirely deprived of its metallic principle, and 
that its super-oxigenation renders it reducible and refrac- 
tory. 
The arts may draw some advantage from these oxides, 
by using them in pigments for buildings. I succeeded 
after many washings, in extracting from them a beautiful 
Vol, II. h ' h 
