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Digital Archive of Toyo Bunko Rare Books

CHAPTER XIII.—THE ANALYSIS OF THE METALLIC IMPLEMENTS
AND PRODUCTS OF CORROSION.

In making choice of methods for the analysis of the metallic implements
and products of corrosion, the purpose has been to secure results as accurate
and comprehensive as may be with the least expenditure of valuable and unique
material. In many cases the quantity of material employed did not exceed a half
gram, and in some cases was less than that amount. The sample was taken from
the implement in some cases by means of a lathe center-bit without disturbing
exterior outlines, in some cases was broken from an end or edge, and in many cases
was scraped or flaked off from the surface of the implement or broken from a mass
of corroded material.

THE ANALYTICAL PROCEDURE.

I. Treatment of Material.

Of the material an amount approximating 0.5 gram, if so much was available,
was carefully weighed, placed in a small covered beaker, and treated with 10 c.cm.
of nitric acid (sp. gr. 1.42), the action being moderated by cooling when the sample
was metallic and quickly acted upon, and accelerated by warming when the sample
represented corroded material and was slowly attacked. When the action was
complete, it was usual to evaporate the liquid, desiccate the residue at 110° C.,
moisten with nitric acid, take up soluble material in 50 c.cm. of water, treat with
ammonium hydroxide to formation of the soluble copper-ammonium compounds,
heat to boiling, add nitric acid in excess, and filter the insoluble material upon
ashless paper and wash, reserving residue and filtrate for separate treatment.

By desiccating silica was made insoluble, and by treatment with ammonium
hydroxide complete hydrolysis of soluble tin compounds was effected. In some
of the earlier analyses of pure metal the process of desiccation was omitted, and
for the formation of the insoluble metastannic acid reliance was placed upon
dilution and boiling. Experience showed, however, that all the tin is found in
the residue when the ammonium hydroxide treatment is employed, and this
treatment was followed in nearly all the work.

II. The Insoluble Residue after Treatment with Nitric Acid.

The insoluble residue, consisting possibly of antimony oxide, metastannic acid,
silica, undecomposed material, and lead sulphate in case lead and sulphur were
present, was collected upon ashless paper, washed, ignited in porcelain, and weighed.

The residue was covered with a mixture of sodium carbonate and sulphur
in equal parts, and the mass was heated in the covered crucible until the prelimi-
nary fusion was over and sulphur ceased to be volatilized. The mass was boiled
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