May i, 19 1 3] 



NATURE 



229 



of ultra-violet light and of the penetrating rays of 

 radium on various organic and inorganic compounds, 

 and Meyer and Przibram discuss, among other 

 phenomena, the effect of exposure to radium rays in 

 increasing the " Halhvachs effect" in minerals. 



Meyer and Paneth have undertaken a re-investiga- 

 tion of the proportion of a rays in a uranium mineral 

 due to the uranium and radium respectively, which 

 they find to be 100 : 573, instead of 100 : 45, as found 

 initially by Boltwood. The new ratio agrees perfectly 

 with the present view that uranium consists of two 

 elements, uranium I. and II., each emitting one a ray 

 per atom disintegrating, of ranges respectively 2-5 

 and 2-9 cm. of air at 15 , with which the older ratio 

 was seriously in disagreement. 



Lastly, Hess deals with the heat generated by a 

 pure radium salt at the moment of its preparation, 

 when it is free from the products of disintegration, 

 and finds it to be 252 calories per hour per gram of 

 radium (element). In the course of a month, in which 

 the first four products accumulate to the equilibrium 

 quantitv, the heat generated increases by 107-1 cal. 

 per hour, the total (for a and B rays, and 18 per cent, 

 of the 7 rays) agreeing perfectly with his previous 

 measurements in collaboration with Prof. Meyer on 

 a different preparation. As an example of the perfec- 

 tion to which our knowledge of the processes of 

 atomic disintegration has been brought, and to which 

 it would perhaps be difficult to find a parallel else- 

 where in the molecular sciences, it may be mentioned 

 that the figure 25-2 calories per hour per gram of 

 radium agrees, within 1 per cent., with the value 

 deduced from Rutherford's direct measurements of 

 the number, mass, and velocity of the a particles 

 expelled by radium, taking into account the kinetic 

 energv of recoil. An analogy to this would be a 

 determination of the "heat-drop" of steam by count- 

 ing the number, measuring the individual mass, and 

 determining directlv the velocity of the molecules 

 leaving a turbine-jet. F. S. 



SCIENTIFIC WORK OF THE CENTRAL 

 CHEMICAL LABORATORY OF THE 

 ITALIAN CUSTOMS. 



THE report of the year's work of the Central 

 Chemical Laboratory of the Italian Customs at 

 Rome (Annali del Laboratorio Chimico Centrale dellc 

 Gabelle, vol. vi., 1912, pp. xxxvii + 707), under the 

 direction of Prof. V. Villavecchia, which has recently 

 been issued, contains an introductory article by the 

 director on the history of its twenty-five years' activity 

 since its inauguration in 1S85. In this period 225,679 

 analyses have been made, and 1524 special reports 

 prepared for various Government departments, whilst 

 127 original papers have been published in the Annali 

 issued from the laboratory. Recently a museum of 

 commercial products and raw materials has been estab- 

 lished in connection with the Central Laboratory, 

 care being taken to ensure the genuine character of 

 all the specimens, so that they can be used as 

 standards of reference by the Government chemists ; 

 an account is given in the report of the 32,382 samples 

 collected for this museum, and a description of the 

 building. 



In the present report some of the most important 

 original contributions are as follows. I. Barboni has 

 investigated comparatively the different methods which 

 have been used for the analysis of commercial calcium 

 citrate, and reports on their suitability. A. Capelli, 

 in examining the alkaloids contained in mate\ has 

 been able to separate only caffeine, although the 

 statement has been recently made that caffeine is pre- 

 sent onlv in traces, the principal alkaloid being 

 NO. 2 2 70, VOL. 91] 



matteine. There is a series of papers by R. Belasio 

 on the electrolytic estimation of zinc, the separation 

 by electrolysis of iron and manganese, the analysis of 

 white metals and tinfoil, the detection of antimonj 

 and of tin in metallic alloys, and a description of the 

 electrolytic methods of analysis in use in the labora- 

 tory of the Gabelle. Among papers dealing with 

 organic analysis the following may be cited : — G. 

 Testoni, the estimation of sucrose in the presence of 

 other sugars; E. Castaldi, the Halphen test for cotton- 

 seed oil ; L. Settimj, a characteristic colour reaction 

 for soja-bean oil; S. Camilla and C. Pertusi, the 

 detection and estimation of the xanthine bases in 

 cocoa, tea, and coffee; V. Villavecchia and A. Capelli, 

 the quantitative estimation of cotton, wool, and silk 

 in mixed fabrics. 



Independently of its work of routine analyses for 

 the control of commercial and dutiable articles, the 

 laboratory is carrying out valuable work in investigat- 

 ing the many different and often conflicting methods 

 of analysis in current use, and, when necessary, devis- 

 ing new processes to meet freshly arising needs. 



THE HYDROMETER AS AN INSTRUMENT 

 OF PRECISION. 1 



\,|R. J. Y. BUCHANAN publishes in the Trans- 

 '*■*• actions of the Royal Society of Edinburgh 

 (vol. xlix., part i., 1912) the results of extended re- 

 searches on the specific gravity and the displacement 

 of some saline solutions. The memoir, which occupies 

 225 quarto pages, deals with the densities and varia- 

 tions in densities of certain groups of saline solutions ; 

 but although the results obtained are themselves of 

 interest and value, the importance of the work centres 

 rather in the detailed study of the use of the hydro- 

 meter as an instrument for work requiring a high 

 degree of accuracy. This importance, of course, arises 

 mainly from the fact that ever since the days of the 

 Challenger expedition, Mr. Buchanan has been the 

 principal champion of the hydrometer method for 

 determining the specific gravities of samples of sea- 

 water for purposes of oceanography, and that the 

 method has now for many years been practically 

 disused by most oceanographers. 



Two forms of hydrometer are described. In the 

 "closed" tvpe — that ordinarily used for, e.g.. sea- 

 waters — the weight of the instrument is varied by 

 adding to or subtracting from a number of weights 

 placed on the top of the glass stem of the hydrometer. 

 The additional weights are obviously limited by ques- 

 tions of stability, for if too much weight. is accumu- 

 lated at the top of the stem the whole instrument will 

 tend to capsize. Solutions of high density are there- 

 fore treated with an instrument of the "open" type, 

 in which the stem is left open at the top instead of 

 being hermetically sealed, and the paper scale is re- 

 placed by one etched on the stem itself. The internal 

 ballast can then be altered by varying the amount of 

 mercury or the number of lead pellets, as the case 

 may be, and the final adjustment by weights at the 

 top of the stem made without risk of the instrument 

 swinging out of the vertical. 



Every worker with the closed type of instrument 

 (that used on board the Challenger) knows that the 

 real difficulty is not to get consistent results, but to get 

 accurate results, or results which will either agree with 

 those obtained by other methods or differ from them in 

 some way which can be accounted for. Much labour 

 has been expended by many investigators in efforts 



1 " Experimental Researches on the Specific Gravity and the Displacement 

 of Some Saline Solutions.'' By I. Y. Buchanan, F.R.S. (Trans. R.S.E., vol. 

 vli.v., part i., rqi2.) Pp. 227. (Edinburgh: Neill and Co, Ltd., 1012. 

 Price -js. 6if. net. 



