August 28, 1913] 



NATURE 



66 = 



It is hoped that both of these parties may be 

 arranged by about the middle of November, while 

 the organising secretary for the Australian meet- 

 ing (Dr. A. C. D. Rivett) is in England. Inquiries 

 should be addressed to the .Secretary, British 

 Association, Burlington House, Piccadilly, W. 



TWENTY-FIVE YEARS' WORK AT THE 

 PHYSIKALISCH - TECHNISCHE REICHS- 

 ANSTALT, CHARLOTTENBURG. 



""PHE Physikalisch-Technische Reichsanstalt, 

 -»■ which may be aptly termed the German 

 " National Physical Laboratory," plays such an im- 

 portant part in physical science that it may not 

 be without interest to readers of Nature to in- 

 dicate briefly a few of the more prominent ques- 

 tions which 'have been dealt with at the institu- 

 tion since its foundation in 1885, which, by the 

 way, was due in great measure to Werner von 

 Siemens. Considerable information is afforded 

 in two articles ] recently published by members 

 of the staff, and these papers should make inter- 

 esting reading to those desiring further particulars 

 of the work. • 



In addition to carrying out research work of 

 direct interest to science and industry, the 

 Reichsanstalt carries out the verification against 

 standards of all kinds of instruments in the same 

 manner as does the National Physical Laboratory 

 in this country. It is, however, the research work 

 to which we will confine ourselves here. The re- 

 markable growth in the activities of the institu- 

 tion has kept pace with the advancement in 

 scientific research during the last quarter of a 

 century. 



Dealing first with heat, the Reichsanstalt has 

 occupied itself with practically every question in 

 this branch of physics. One of its first tasks 

 after getting into working order was the con- 

 tinuation of Regnault's famous work : he had 

 shown that the scale of the mercurial thermometer 

 could not be used as a standard owing to the 

 influence exerted on the readings of the instru- 

 ment by the expansion of the glass tube, the 

 indications differing considerably in the range 

 above ioo°C. with thermometers made of differ- 

 ent sorts of glass. Great difficulty had been ex- 

 perienced in finding a glass suitable for high 

 temperatures when the Reichsanstalt commenced 

 operations. Schott and Genossen, of Jena, ex- 

 perimented with different types of glasses and 

 produced thermometer tubes constructed of new 

 types of glass, and the Reichsanstalt tested these 

 tubes as regards their accuracy over the funda- 

 mental interval o-ioo°C., and their suitability for 

 higher temperatures. The result is that the well- 

 known Jena 59 quality has up to the present 

 proved the most suitable in respect of small 

 thermal expansion and of robustness. Extensive 

 comparisons were afterwards carried out between 

 the mercury thermometer and the air thermometer, 



1 "Die Physikalisch-Technische Reichsanstalt: Funfundzwanzie Jahre 

 ihrer Taligkeit." By Pri's. Scheel, Holborn, Ja-ger, and Brodhun. Die 

 Naturwissenschaftcn, 1913, Nos. 8, 10. 12, 14. 



" Die Physikalisch-Technische Reichsanstalt in Charlottenburg." By 

 Prof. Karl Scheel. Akademische Rundschau, January, rqri. 



NO. 2287, VOL. 91] 



owing to the difficulty experienced in realising the 

 hydrogen thermometer scale at temperatures above 

 ioo°C. These measurements were carried to 

 500 C. At the present day nitrogen-filled thermo- 

 meters are recognised as the most practical for 

 high temperatures, and their success is to no 

 small degree due to the labours of the Reichs- 

 anstalt. The institution has also played a not 

 inappreciable role in the development of pyro- 

 metry, from the introduction of the thermo-couple 

 by Le Chatelier to the more recent progress which 

 resulted in the introduction of radiation pyro- 

 metry, based on the early observations of 

 Becquerel, and on the later investigations of Kirch- 

 hoff and Wien on the subject of "black body" 

 radiation. Following on Regnault's experiments, 

 the Reichsanstalt has carried out research on the 

 thermal properties of substances : this included 

 experiments on the expansion of water between 

 o° and ioo° by the communicating tube principle, 

 and the determination of the saturation pressure 

 between — 6o° and + 370°C. The determination 

 of the specific heat of gases — a question of high 

 importance in internal combustion engine work — 

 has been carried out with nitrogen, carbonic acid 

 gas, and water vapour up to I400°C., thus com- 

 pleting the work of Le Chatelier and Mallard in 

 this connection, and the determination of the 

 specific heat of gases at low temperatures has been 

 made by Callendar's continuous flow method, im- 

 proved by the counter-flow principle. 



The electrical side of the work is no less interest- 

 ing, and the activities of the institution have kept 

 pace with the unceasing progress of this all- 

 embracing science. It is, of course, of prime im- 

 portance that the electrical units of measurement 

 should be defined and realised as accurately as 

 possible, and in this connection the Reichsanstalt 

 has taken part in international conferences dealing 

 with the subject, as well as cooperating with the 

 State laboratories of other countries in carrying 

 out measurements. Mercury copies of standard 

 resistances had been found to be inconvenient in 

 practice, and resistance boxes of German silver 

 had proved inconstant and shown the resistance to 

 be an intimate function of the temperature. It 

 was Weston, in America, who first paved the way 

 to improvement in this respect by inventing an 

 alloy which showed but slight change of resist- 

 ance with temperature ; but it was left to the 

 Germans to improve on Weston's discovery, the 

 result being the introduction of the alloy (copper 

 eight parts, nickel four, and manganese twelve) 

 known universally as "manganin." Twenty years' 

 experience at the Reichsanstalt with manganin 

 resistances has shown the material to be unsur- 

 passed by any other. 



At the time the Reichsanstalt was founded 

 standard cells were scarcely in use : it was only 

 in the 'nineties that the Reichsanstalt, as the result 

 of investigations, produced a practical standard 

 cell, and one capable, moreover, of undergoing 

 transit. This cell has, however, been superseded 

 by the well-known Weston normal cell, which was 

 accepted as the standard of e.m.f. by the London 



