10
wall with the composite sample. Altogether, 15 of the slabs were 12.001 or over, and 16 of them were below this figure; that is to say that over half of them failed to pesa as No.1 tir, although the batoh as a whole assayed over 391.
4.
It is clear, then, that there exists hare a reasonabla explanation of the 1ifferences between the Hong Kong and Lonton aagays. Taking a 10% sample in each case, it is probable that both samples will give a fair repræsentation of the quality of the parcel. But there is always the possibility that one sampler may hit on a majority of the goci glebs for his sample, and the other take mostly bad ones. Then this happers the two assayers will not agree. It would bɔ of the greatest intarast to compare the corresponding figures obtained in London and Hong Kong for a large number of parcels; it seems probable that they would seldom agres very closely, and that the London figure would be higher than the Hong Kong one as often as the reverse is the caso.
With a view to settling the matter finally, it is suggested that the London Metal Exchange should instruct its London 28sayers to carry out a series of analyses on a suitable parcel of tin, similar to that one in Hong Kong. If the Hong Kong results are thereby confirmed, it will be necessary to decide whether a more comprehensive method of sampling would justify the extra expense involved. The 1199l mathod would be to take a simple from every elab in the parcel and bulk these for aggay, but the cost of such en operation would be prohibitive. But until etaps are taken to ensure that the samples are truly representative of the parcels, it is useless to insist upor two ascays by well known assayers, or to expect the London and Hong Kong figures always to agree.
8.
It is again emphasised that the Hong Kong Government Laboratory in no casa accepts any responsibility for these percels of tin which it se plas and asgavs, and its certificate carries no sort of guarantee. The 388ays are done at the request of the Hong Kong exporter, to ensure that he is receiving tin of a certain degree of purity from the rafiner; The Government Laboratory acts as a firm of ocnsulting analysts and charges a fee for the seaye. There is no control over the production or shipping of the tir.
Attention is again invited to Mr Branson's Report to the Colonial Office on this subject.
NOTE.
Up to the Summer of 1235 the chief impurity in the ting was 1991, 0.5-0.9%, together with small amounts of arsenic, antimony, iron, copper, and bismuth. It was then noticed during the solution of the metal for analysis, that there was an increasing amount of a black slowly scluble residue, which was recognised as being due to antimony. Subsequent full analysis shored this to be the case, and the impurities now were lead, 0.4-0.8%, antimony, 0.05-0.3%, and traons of the other matale as before.
Page 10Page 11
No comments yet.
Private notes are available after approval.