A WELL EQUIPPED CHE^IICAL LABORATORY 



i^i 



FIG. 



>i FRESHLY 

 MIUM. 



CAST CAD- 



tion of cadmium iodide, the metal ap- 

 peared, under a magnification of one 

 hundred diameters, as shown in Fig. 2. 



That we are, in fact, dealing with 

 allotropic modifications of cadmium 

 can no longer be doubted. Further- 

 more the change in crystalline form is 

 from a lower to a higher degree of sym- 

 metry, which is as it should be, if the 

 freshly cast metal is to be more electro- 

 positive than the gray modification. 



Other lines of evidence are being 

 accumulated to confirm the correctness 

 of the view that cadmium exists in at 

 least two allotropic modifications. 



It is of interest to point out that simi- 

 lar results have recently been obtained 

 bv Professor Ernst Cohen of Utrecht, 

 Holland. 



He has succeeded in showing that 

 ordinary freshl}^ cast cadmium consists 

 of a mixture of three allotropic modifi- 

 cations which he designates as a, b. and 

 2 cadmium. 



In addition to the investigation of 

 cadmium, similar studies are being 

 carried out with lead. While it would 

 be premature to make any detailed 

 statement at this time yet it may be of 

 interest to point out that there is un- 

 questionable evidence in favor of the 

 allotropjsm of lead. This is clearly 

 shown by Figs. 3 and 4. In Fig. 3 is 

 shown a photomicrograph of a freshly 

 cast lead surface magnified one hun- 

 dred diameters, while in Fig. 4 the 

 same surface is shown after six weeks 

 immersion in a solution of lead acetate. 



the magnification being one hundred 

 diameters. 



The complete disintegration of the 

 metal is clearly shown in Fig. 4. 



The question that the visitor to the 

 Hillside Laboratory invariabl}^ asks is, 

 'A\'hat is the practical bearing of all 

 this work"? 



To this Dr. Getman invariably replies 

 that he does not know, — rthat it fre- 

 quently happens that discoveries, 

 which at the time when they are made 

 are of purely scientific interest, turn 

 out later to have practical application 

 and hence commercial value. 



In writing to the Faraday Society of 

 London about his work along similar 

 lines. Professor Cohen has this to say : 

 "****A new field of research for chem- 

 ists, as well as for physicists, presents 

 itself. Whilst it will be the task of the 

 chemist to prepare the pure modifica- 

 tions (of the metals) and study their 

 physicochemical properties, the physi- 

 cist will require to turn his attention 

 to the determination of their physical 

 and mechanical constants. As the phe- 

 nomena described have been unknown 

 up to the present, metallurgists have 

 not been able to take them into account 

 when studying the hardening of metals. 

 And yet these reversible transforma- 

 tions, which so often go on so very 

 slowly in consequence of the retarda- 

 tions mentioned above, must play an 

 important role when the metals are 

 subjected to changes of temperature. 



FIG. 2. SURFACE OF CADMIUM AFTER IM- 

 MERSION IN A SOLUTION OF CADMIUM 

 IODIDE. 



