Dr. Wollaston on metallic titanium. 19 
tinued heat oxidates them, and they become purple or red 
at the surface, according to the degree of oxidation, or depth 
to which it penetrates. 
Borax has no action upon them, but only cleans the sur- 
face from any oxide that may be formed. Neither does the 
addition of subcarbonate of soda produce more effect than 
borax alone. 
Nitre, aided by a strong heat, oxidates them rapidly ; but 
unless the heat be long continued, the effect is only super- 
ficial. 
The combined action of nitre and borax together, soon 
effects their solution, as the latter dissolves the oxide as fast 
as it is formed, and presents a clean surface for fresh oxida- 
tion. But as these salts do not unite by fusion, the addition 
of soda, as a medium of union, considerably shortens the pro- 
cess. The fused mass becomes opake in cooling, by the de- 
posit of a white oxide, which may either be previously freed 
of the salts by boiling water and then dissolved in muriatic 
acid, or the whole mass may be at once dissolved together. 
In either case alkalies precipitate from the solution a white 
oxide, which is not soluble by excess of alkali, either pure, 
or in the state of carbonate. By evaporating the muriatic 
solution of the oxide to dryness, at the heat of boiling water, 
it is freed of any redundant acid, and the muriate which re- 
mains is perfectly soluble in water, and in a state most fa- 
vourable for exhibiting the characteristic properties of the 
metal. 
Infusion of galls gives the well known colour of gallate of 
titanium. The colour occasioned by adding triple prussiate 
of potash is red, as observed by Laugier, and so nearly re- 
