ON THE SAMPLING AND ASSAYING OF CHIN SH
NO.1 TIN.
SUMMARY.
1.
Complaints have been received in Hong Kong ovar a number
of years from Lonion firms of metal importers, to the effect that
parcels of tin exported from Hong Kong as 33% tin or over, a88BayeⱭ under 296 when received. All the parcels in question consisted of
small 38lb. slabs. The Hong Kong assays were carried out by the
Government Laboratory, and the complaints received implied that
the discrepancies between the Hong Kong and London assays were the fault of this laboratory.
2.
Following an increasing number of such complaints in 1933- 1935, a detailed investigation was carried out in Hong Kong to find the cause of the discrepancies. In 1235 @ivantage was taken of the presence in England of the Government Analyat, Mr. V.C.Branson, to
investigate the matter in London. A serious error was found in the
method of sampling employed in London, and this was rectified by the London Metal Exchange. Complaints regarding these shipments of
small slabs have ceased since that time. (See Kr. Branson's Report
on the matter to the Colonial Office.)
3.
Shortly before Mr. Branson's return to Hong Kong, a
complaint was received raferring to a parcel of large lowt. slabs,
and as a result, further work was carried out on the subject in
Hong Kong. The methods of refining employed there were stuiiei,
and it was concluded that it would be possible for the individual slabe in a large parcel of tin to vary considerably in composition
amongst themselves. This conclusion was tested and fount to be
correct.
It follows that there will always be the possibility of
discrepancies in the assays arising from this cause. It is suggested
that the London Metal Exchange should authorise its London assayers
to carry out certain analytical work on the lines of that done in
Hong Kony. If the Hong Kong results are thereby confirmed, the
question as to whether the method of sampling should be altered to