March 3, 1899.] 



SCIENCE. 



337 



proved the little known method of Puluj for 

 measuring inductance by means of alternating 

 currents. The method of Puluj was devised 

 independently by Professor S. T. Moreland and 

 reported to Section B at the Boston meeting of 

 the American Association. The method, in its 

 simplest form, is to connect two circuits in par- 

 allel between alternating current mains and ad- 

 just nou inductive resistances until the currents 

 in the two branches are in phase, when the in- 

 ductances in the two branches are directly as 

 the resistances. To show when the currents 

 are in phase an instrument called a phase indi- 

 ■caior is used. This instrument is essentially a 

 small induction motor without iron. It con- 

 sists of two small coils with their planes vertical 

 and at right angles to each other, surrounding 

 a suspended aluminum or copper rod. These 

 coils are connected, one in each circuit, and 

 when the two currents are not in phase 

 with each other the suspended rod is deflected. 

 Martienssen modifies the instrument by wind- 

 ing one coil with two strands of wire, each 

 strand being provided with separate termi- 

 nals. One of these strands he connects in cir- 

 cuit as before, and the other constitutes a sec- 

 ondary coil in which a current is induced by the 

 current in the primary strand. This induced 

 current is sensibly in quadrature with the 

 primary current, and by the use of an adjust- 

 able non-inductive resistance in this secondary 

 circuit the instrument may be used, according 

 to Martienssen, for the accurate measui'ement 

 of much smaller inductions. 



Puluj 's method, as modified by Martiens- 

 sen, is a zero method ; it requires only a 

 single adjustment ; it does not require har- 

 monic electromotive foi'ce, nor does the fre- 

 quency of the e. m. f. need to be known ; and 

 it gives accurate results for inductances ranging 

 from a few hundreds to many millions of cen- 

 timeters. In short, we seem to have at last a 

 feasible laboratory method for the accurate 

 measurement of inductance. 



W. S. F. 



NOTES ON INORGANIC CBEMISTBY. 

 An interesting discussion has been carried on 

 during the last few years as to the constitution 

 of inorganic compounds, especially of the 



metal-ammonium bases, by Pi-ofessor S. M. 

 Jorgensen, of Copenhagen, and Professor 

 Alfred Werner, of Zurich. Professor Jor- 

 gensen, to whom we owe so much of our 

 knowledge of these bases, especially those of 

 cobalt, chromium and rhodium, defends the 

 constitution based on the present ideas of 

 valence, which has been developed in its ap- 

 plication to these compounds largely by him- 

 self on the basis furnished by Blomstrand. 

 Professor Werner, feeling the insufficiency of 

 the theories of valence to account for most of 

 our complex inorganic compounds, has pro- 

 posed a new theory of coordinated groupings, 

 in which he seeks to account for the constitution 

 not merely of the metal-ammonium bases, but 

 also of all the complex inorganic compounds, 

 including those containing water of crystalli- 

 zation. The last number of the Zeitschrift fur 

 anorganische Chemie contains the eleventh paper 

 by Jorgensen and the fifteenth paper by Werner. 

 In the former Jorgensen reviews Werner's 

 theory, replies to all the objections Werner has 

 raised to the valence theory as applied to the 

 metal-ammonium compounds, shows the in- 

 sufficiency of Werner's theory, and finally, by 

 an ingenious piece of chemical logic, shows 

 that Werner's own theory must, if consistently 

 carried out, lead him to Jorgensen's own for- 

 mulae for these compounds. In this paper, and 

 that of Reizensteiu, recently mentioned in this 

 column, one may get a good view of the argu- 

 ments on both sides of the controversy. 



Werner's paper in the same number of the 

 Zeitschrift is confined to a study of the appli- 

 cation of his theory to the double chlorids. 

 He has tabulated all the double chlorids from 

 the whole field of chemical literature, and 

 grouped them in types according to his theory, 

 considering also the water of crystallization 

 present. 



It is yet too soon for any final judgment to 

 be pronounced on Werner's theory, especially 

 because the field to which it applies is so im- 

 mense. The limitations of the valence theory 

 are, however, only too keenly felt by chemists, 

 and Werner's work is leading in the right di- 

 rection. At all events, this lengthy controversy 

 is productive of much good. It has turned the 



