KNOWLEDGE c^- SCIENTIFIC NEWS. 



[Sept., 1905. 



CHEMICAL. 



By C. .■\iNS\voKTn Mitchell. H.A. (0.\on.), F.I.C. 



On Antimony in R.\jbber Rings. 



A r.AKAGKAi'H with the sensational heading •• Poison in 

 Stoppers " appeared recently in one of the daily papers, and 

 purported to be an interview with a Liverpool doctor. This 

 gentleman was reported to have examined the red rubber 

 rings so largely used for the stoppers of mineral water bottles, 

 and to have asserted that a poisonous dose of antimony could 

 be removed from them by a simple washing with cold water. 

 In fact he is stated to have attributed many deaths within his 

 own experience to this cause. .\s such stoppers have been in 

 use for over 30 years, and are now almost universally em- 

 ployed, the question is one of the greatest importance, and the 

 present writer has therefore made experiments to determine 

 the degree of truth in the charges here brought against them. 

 These red rings certainly contain a large proportion of anti- 

 mony in the form of the pentasulphide, and it is to this that 

 they owe their colour. O'lantitative determinations showed 

 that the proportion of this pigment in the rubber amounted to 

 15 per cent, or more. Experiments were next made to dis- 

 cover to what extent this antimony was soluble. The rings 

 were boiled for over an hour with water, but absolutely no 

 trace of antimony could be detected in the liquid. .As it 

 seemed possible that in practice the rubber of the rings might 

 become worn and fragments fall into the bottle and so be in- 

 advertently swallowed, parallel experiments were made with 

 hydrochloric acid of 10 per cent, strength, i.e., much stronger 

 than the acidity of the gastric juice ; but in this case, too, the 

 liquid was quite free from antimony. This is not surprising, 

 since it is well known that antimony pentasulphide is only 

 soluble in alkalies and concentrated acids ; and hence it would 

 seem that there must be some error in the report about the 

 stoppers examined in Liverpool. .-Xt the same time it would 

 be advisable for the manufacturers of the rings to replace 

 antimony sulphide by some pigment above suspicion. For 

 although as at present employed the rubber-ringed stoppers 

 may be regarded as quite safe, there are conceivable cases in 

 which the antimony might be brought in solution — t'.^., by con- 

 tact with strong potash. The effects of antimony upon the 

 system are ver>' similar to those of arsenic. Both are irritant 

 poisons, and both are cumulative in their action. It is well 

 known that the dead bodies of the Styrian arsenic eaters 

 remain undecomposed for years, and this preservative effect 

 is also a characteristic of antimony. 



The Formation of Radium from Uranium. 



A very interesting discovery made by Mr. F. Soddy fur- 

 nishes new evidence in support of the now generally accepted 

 view that one element can, under certain conditions, be trans- 

 formed mto another. A solution containing over 2 lbs. of 

 uranium nitrate was freed from all radium that it contained 

 by repeated precipitation, and was then kept for 18 months in 

 a closed bottle. It was examined from time to time, and it 

 was found that it gradually acquired the power of emitting an 

 emanation absolutely identical in characteristics with that given 

 off by radium. Hence the conclusion was arrived at that the 

 uranium was very gradually transformed into radium, though 

 only traces of the latter substance were present in the solution 

 at the end of the period of observation. 



Thorianite : A New Mineral from Ceylon. 



( )n<: of the most valuable minerals known has recently been 

 examined by Professor I )unstan and .\Ir. Blake at the Imperial 

 Institute. It is found in the form of small dark cubical 

 crystals in gem-bearing deposits in rivers in Ceylon; the 

 principal source being the bed of the small stream, Kuda 

 Pandioya, but it is not known from what kind of rock the 

 deposit is derived. The mineral varies in colour from dull 

 grey to dark brownish-black, and many of the crystals have a 

 polished appearance from having been worn in the bed of the 

 river. It is nearly opaque, except in very thin layers, is very^ 

 infusible, and becomes strongly incandescent when heated to ' 

 a high temperature. Its- density is about 97. It can be: 



readil)' powdered, and dissolves easily in dilute sulphuric 

 acid, yielding a gas which consists mainly of helium. It is 

 composed principally of thoria (thorium dioxide), the amount 

 of which ranges from about 70 to So percent. It also contains 

 from 10 to 12 per cent, of uranium oxide and rare earths, and 

 smaller amounts of oxides of lead and iron. One specimen 

 was found to contain 0-39 per cent, of helium. The com- 

 mercial value of thorianite is due to the free thoria, which is 



Action of Thorianite on a Piiotographtc Plutc In tlic Dark. 



used in the manufacture of mantles for incandescent gas 

 burners. Hitherto the chief source of this oxide has been 

 monazite sand, which contains only a small percentage of 

 thoria. Consignments of the new mineral from Ceylon have 

 been sold in this country for as much as ^Tisoo per ton. 

 Kadium has been identified in thorianite, which is one of the 

 most radio-active substances known, though it is not quite so 

 active as some of the pitchblendes examined by NIadame 



RadioKrapli of a .sliillinK lukcn tlirouKli I'uper by meani uf Tflorianitc. 



Curie. The present writer has had the opportunity of examin- 

 ing a number of specimens of thorianite and testing their 

 radio-activity, and some of the results are shown m the 

 accompanying figures. In the first case the thorianite was 

 sprinkled over the photographic plate and left for 12 hours in 

 the dark, and in the second experiment a shilling was placed 

 on the plate and covered with paper, on which the mineral 

 was scattered. It is interesting to note that the radiations 

 must have been reflected beneath the coin in such a way as to 

 obtain an image of the device. 



