466 Frederick Guthrie on Eutexia. 



§ 203. Again, a tetra-eutectic is obtained either by building 

 up from the tri-eutectic and a metal, or from three eutectics ; 

 or perhaps more readily, although with greater waste of metal 

 in the first tentative experiment, by fusing the four metals 

 together. The three eutectic bismuth alloys above described 

 w T ere fused together in considerable quantity and in indefinite 

 ratio. As the mass had only partly solidified at 100°, it was 

 pressed in a linen bag under boiling water. The liquid por- 

 tion was further cooled. A large amount remained liquid at 

 71° C. ; at which temperature the thermometer thenceforth 

 stood until the whole was solid. On remelting several times, 

 and collecting that which remained liquid after about a fifth 

 had solidified, the eutectic alloy of bismuth-tin-lead-cadmium 

 was obtained pure. It showed the following composition: — 



Bismuth .... 47-45 47-38 



Lead 19*39 19-36 



Cadmium .... 13-31 13-29 



Tin 20-00 19-97 



100-15 100-00 



The question, very interesting to mineralogists, immediately 

 arises, Can a tetra-eutectic alloy be made without loss by 

 mixing three dieutectic alloys in some proportion w T ith one 

 another ? The answer is in this case certainly in the negative. 

 For according to § 199, 19*36 of lead require 24*25 of bis- 

 muth. Again, according to § 200, 13*29 of cadmium require 

 19*27 of bismuth, and according to § 198, 19*97 of tin require 

 17*08 of bismuth. So that to satisfy the three metals lead, 

 cadmium, and tin eutectically, 60*52 of bismuth would be re- 

 quired, instead of 47*45. 



The above alloy is extremely closely grained and brittle. 

 It may, however, be bruised and rolled. It takes a high polish. 

 When in some thickness its fracture is conchoidal, exposing 

 steel-grey surfaces. This highly eutectic alloy may find uses 

 in the arts, as with the exception of alloys containing mercury, 

 and those of potassium and sodium, it has a melting-point 

 lower than any alloy before described. 



§ 204. The above experiments, in which bismuth replaced 

 the ice of my previous experiments with salt-solutions and 

 some other metal replaced the salt, are of course only a few 

 of an innumerable series of series. But they will serve to 

 show the genesis of bodies of this class. I have already* 

 pointed out how the " de-leading " of the lead-silver alloy in 

 Pattinson's process is really analogous to the separation of 



* R. Inst. Lecture, Feb. 16, 1877. 



