8o 



NA TURE 



[May 26, 1904 



LETTERS TO THE EDITOR. 



{The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous coninninications.] 



Relation between Uranium and Radium in some 

 Minerals. 



In the course of an investigation which I am conducting 

 on uranium-bearing minerals, the detailed results of which 

 will be published shortly, I have come upon a point which 

 seems to be of sufficient interest to warrant immediate 

 publication. This is the close agreement between the 

 amount of uranium and the amount of radium present in 

 those minerals which have been examined. 



The method which has been employed is briefly as 

 follows ; — A weighed quantity of the powdered mineral is 

 introduced into a small glass bulb, which is connected with 

 a larger bulb by a short tube. Attached to the bulb con- 

 taining the mineral is another small bulb containing a 

 small quantity of a suitable acid. The whole apparatus is 

 sealed up at a slightly diminished pressure, and jjy tilting, 

 the acid is brought into the bulb with the mineral, and 

 the complete decomposition of the latter effected by gentle 

 heating. At the end of a couple of days the larger bulb 

 is sealed off from the smaller and allowed to stand for two 

 hours to permit any rapidly decaying emanation which it 

 may contain to dissipate. A small quantity of strong 

 sodium hydroxide solution is introduced into the bulb, and 

 the walls are thoroughly wetted in order to remove the acid 

 fumes. The air contained in the bulb is then transferred 

 to an air-tight electroscope and the rate of leak measured. 

 In comparing the results obtained with different minerals 

 the rate of leak at the end of three hours has been chosen, 

 since at this time the rate of decay of the excited activity 

 and its rate of formation are in equilibrium, and the read- 

 ings of the electroscope are constant over considerable 

 periods. The quantity of uranium in the solution is deter- 

 mined by analysis, and the ratio between the volumes of 

 the two parts of the apparatus determined by measuring 

 their separate capacities. 



The results which have been obtained are as follows : — 



No. 



Substance 



divis 



Nos. I, 2, 3 and 5 from North Carolina; No. 4 from 

 Branchville, Conn. 



The slightly low value of the constant in No. 3 can be 

 explained by the fact that this mineral at ordinary tempera- 

 ture gives off constantly a sinall proportion of its emanation, 

 and is therefore not in complete equilibrium. 



These results show a direct variation from those obtained 

 by Mr. Strutt {Proc. Roy. Soc, Ixxiii., 191), which may 

 perhaps be explained by the fact that he secured the eman- 

 ation by heating his minerals. Experiments which I have 

 made show that on heating samarskite to low redness only 

 10 per cent, of the total emanation is given off, and that 

 heating to bright redness releases only 20 per cent, of the 

 total emanation obtained when the very finely powdered 

 mineral is completely decomposed by heating with concen- 

 trated sulphuric acid.v Bertram B. Boltwood. 



139 Orange Street, New Haven, Conn., U.S.A., May 7. 



The Source of Radium. 



As the subject of the origin of radium is being discussed, 

 I may perhaps be permitted to make a suggestion. 



The source of radium is at present being looked for on 

 the assumption that it is the disintegration product of a 

 substance of higher atomic weight. If this is so, we have 

 apparently to choose between uranium and thorium. Mr. 

 Soddy's experiment throws serious doubts upon the former 



NO. 1804, VOL. 70] 



being the source. The products of the latter appear to 

 have been sufficiently far traced to render it doubtful that 

 it can be the source, .'\gain, the element thorium seems 

 to be scarce in, or even absent from, some radio-active 

 pitchblendes, if the older analyses are to be relied upon. 



I would suggest that radium may not be derived purely 

 as a disintegration product, but as an atomic combination 

 of radio-active products witli some of the elements present 

 in pitchblende. Thus radium would represent the synthesis 

 of an element, not its decomposition. On this view some 

 of the radio-active products of uranium (or thorium) can, in 

 virtue of their great kinetic energy, enter into the atoms of 

 intermixed substances, such as barium, bismuth, &c., giving 

 rise to the new atom radium. The new atom is, however, 

 not very stable, and is consequently shopt lived. Hence 

 its radio-activity. 



If this hypothesis is correct, we should seek to observe 

 the genesis of radium not in any one of the radio-active 

 elements, but in molecular intermixtures of these with the 

 various bodies we know to be conspicuously present in pitch- 

 blende, seeking among the various combinations for a 

 positive result. The quantities of radium (or its emanation) 

 to be expected as generated in a given time remain, of 

 course, the same as on the hypothesis of disintegration ; 

 tlius the experimental investigation presents no additional 

 difficulties beyond its greater prolixity. J. Jolv. 



Trinity College, Dublin, M^y 17. 



As Mr. Soddy is absent from England, it may be per- 

 mitted to me to comment on Prof. Joly's letter. The idea 

 had occurred to us ; but, as remarked, the e.xperiments would 

 be very " prolix." 



A more promising field of research appears to be to try 

 to ascertain whether the immense amount of energy evolved 

 in various forms during the disintegration of the radium 

 emanation may not be able to cause chemical change of a 

 constructive nature ; for example, to change bromine into 

 iodine. An attempt has been made to see if this was the 

 case, but without a positive result. That iodine would be 

 the product of an addition of energy to bromine is 

 of course a mere guess ; but iodine is easily tested 

 for, and hence the experiment. The difficulty will 

 be in recognising with certainty the product of any such 

 change, for the quantity of matter to be produced is, of 

 course, extremely small. It is only, however, by such 

 " mad " experiments that the capabilities of the radio-active 

 bodies can be ultimately gauged. William Ramsay. 



Radio-activity of Russian Muds and Electrification of 

 Air by Metals. 



The researches of Elster and Geitel {Phys. Zeitschr., v. 

 p. 11) having led to the detection of radio-active power in 

 the fine mud or " Fango " of the Italian watering-place 

 Battaglia, induced me to undertake a study of the Russian 

 muds in this character. Out of the five kinds of muds 

 hitherto obtained by me and studied in a desiccated state, 

 two muds, viz. that of the Odessa Kooyalnitzky Liman and 

 that of Arensburg, on the Isle of Oesel, have proved 

 undoubtedly to possess radio-activity, the first being radio- 

 active in a higher degree than the second. In these re- 

 searches we proceeded in a manner quite analogous to that 

 of Messrs. McLennan and Burton in studying the electrical 

 conductivity of the air (Phil. Mag., v. p. 699, 1903). The 

 present experiments were carried out with the most active 

 participation of Mr. Athanassieff. 



We employed two cylinders, a brass one 83 cm. in 

 diameter and 20 cm. high, and another of zinc, 22-5 cm. 

 in diameter and 35 cm. high. In each cylinder there was 

 fixed along the axis a brass wire which was supported by 

 an amber cylinder placed in a brass guard tube. The latter 

 was connected with the earth, and embedded in an insulating 

 ring put into an opening of the upper base of the cylinder. 

 The wire of either cylinder could at will be connected with 

 one pair of quadrants of a Dolezalek electrometer, the other 

 pair being connected with the earth, and the leaf was 

 charged to 100 V by means of a battery of storage cells. 

 The wire, also of brass, connecting the cylinder wire with 

 the electrometer, and the point of connection of that wire 



