CO129-556-18 Chinese tin- reports on analyses 1-7-1936 - 20-10-1936 — Page 8

2.

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make it more comprehensive must be considered.

5.

There is no ground for blaming the Hong Kong Government

Laboratory for these discrepancies in the 998уs. Voreover, it

cannot be too emphatically stated, the Hong Kong Government

Laboratory in no cas accents any responsibility for these parcels

of tin, rer does ita certificate carry any sort of uarantee.

REPORT.

1.

Complaints have been received in Herg Keng over a number of years from London firms of matal importare, to the effect that the assays done on certain parcels of Chinese No.1 Tin in Hong Kong, do not agree with the sesays ss11 to be done on the same parcels on arrival in England. The London firma invariably complained that the Hong Kong assays gave higher figures than the London cnes, and that tins which hai passat as No.1 in Hong Kong failed to say 30% in Lonion. Although similar shipments of tin that have been assayed in Hong Kong have gone to many other ports in the world, complaints of this nature have been received from Lcnlon alone.

?.

During the years 1933-35 an increasing number of such complaints was racaival. Whenever possible the samples cf tin in question wera ra-a88ayed, and in no case WAS 3 result 11fferent from that originally found obtained. In several ca998, moreover, samples ware archanged with the London a8@ayers, and analyses of the same sample invariably agreed closely, even though different mathc18 of analyaia wara employed. It was therefore concluded that these 1ifferent methode gave results agreeing within the limits of experimental error, and the differences in results that have bean the cause of all the trouble have not been due to any fault in these methods, or on the part of the analysts employing them.

The Government Analyst, Mr. V.C.Brengon, eng on leave in England in 1935, and advantage was taken of his presence in London for him to investigate the matter there. In this he had the assistance both of the London Metal Exchange and of Messrs. Dariel C.Griffiths & Co., the asanyera who had analysed many of the parcela that had given rise to complaints. An examination of the methods of sampling employed quickly led him to discover one very erave source of error, for whereas in Hong Kong 10% of the glaba of tin are sample, irrespective of size, in Lonion one elab was sampled in each 100rt. draft. This latter method gave a lo sample when dealing with lowt. slabs, but when the draft consisted of amall sclb. slabs, a 'slab sarpla' of 90% only was obtained. As all the parcels that had given rise to complaints hai consisted of the89 281b. slabs, it was concluded that this error in the sampling in Lonion was respon sible for the 1ivergent figures obtained by the two assayers. This conclusion is indicata in Mr. Braneon'a Report to the Colonial offion, which Report was forwarded to the London Metal Exchange. The London Yotel Exchange alterad its contract form to eliminata this source of error, and no further complaints have been received as to these porcels of small glabe. (S49 Vr. Branson's Report.)

3.

At the end of 1235, shortly befora Vr. Branson's return to Hong Kong, another complaint of a similar nature was receivei, but referring in this case to a parcel of large lowt. slabs. This is believed to be the firat cocaaien on which such a let hag bean quariat. After careful ocnsileration it was decided that differences in the e-aays of such parcela of large alebs might arise if the slabs differed materially in ocmposition between themselves. Accordingly, a study was made of the methci8 of tin refining employel in Hong Kong, and the means by which these