TRANSACTIONS OF THE SECTIONS. 6/ 



pounds and those which are simple mixtures ; for compounds have special and cha- 

 racteristic properties, whilst mixtures participate in (he properties of the hodies com- 

 posing them. This method of investigating alloys and amalgamshas enabled us to ascer- 

 tain the metals which combine together to form definite compounds, and those which, 

 when melted together, only form mixtures. Thus, for example, bronze alloys are defi- 

 nite compounds, for each alloy has a special conductibility of heat. Thus the alloy — 



Obtained. Calculated*. Difference. 



SnCu 2 13-65 19-87 6-22 



SnCu 3 15-75 21-37 5-62 



SnCu 1 4-96 21-88 10-92 



SnCu 5 6-60 22-50 15-90 



These same alloys have a specific gravity of their own. Thus — 



Obtained. Calculated*. Difference. 



SnCu 2 8-533 8-059 0-474 



SnCu 3 8-954 8'208 0-756 



SnCu 1 8-948 8-306 0642 



SnCu 5 8-965 8-374 0-591 



The same fact is also observed in the expansion or contraction of these alloys ; 

 whilst, on the contrary, the alloys of tin and zinc being mixtures, conduct heat, have 

 a specific gravity, and expand according to theory, or the proportion of tin and zinc 

 which they contain. Thus for heat — 



Obtained. Calculated. Difference. 



ZnSn 2 15-15 14-90 0-25 



ZnSn 16-00 15-80 0-10 



Zn 2 Sn 16-65 16-95 0-30 



Specific Gravity. 



Obtained. Calculated. Difference. 



ZnSn 2 7-274 7-193 0-081 



ZnSn 7-262 7-134 0-128 



Zn 2 Sn 7-188 7-060 0-128 



The authors then gave tables showing the specific gravity of various alloys and 

 amalgams divided under two heads : — 



I. Those which have a higher specific gravity than indicated by theory. Of this 

 class there were five series, viz. copper and tin, copper and zinc, copper and bismuth, 

 copper and antimony, and tin and zinc, — comprising thirty-one alloys. 



II. Those which have a less specific gravity, or expand. Of these there ai-e six 

 series, viz. mercury and tin, mercury and bismuth, mercury and zinc, antimony and 

 bismuth, bismuth and zinc, and tin and lead, — comprising forty alloys and amalgams. 



Their researches reveal two important facts ; first, that there is one metal the 

 alloys of which always contract, viz. those of copper, whilst all the amalgams ex- 

 pand or have a less specific gravity ; secondly, that the maximum expansion or con- 

 traction of alloys and amalgams generally occurs in those which are composed of one 

 equivalent of each metal, the exception being those of tin and zinc. But this arises 

 no doubt from the fact, that all the alloys, with the exception of the latter, are com- 

 pounds and not mixtures. 



In conclusion, attention is drawn to the extraordinary contraction or expansion that 

 some of these alloys experience. Thus, for example, the alloy of three of copper and 

 one of tin, 



Found. Calculated. Difference. 



8-954 8-208 0-746 



whilst the amalgams of tin expand to nearly the same extent, as shown by these 

 results : — 



Found. Calculated. Difference. 



1 of Mercury | 



1 of I in J 



1-004 



* The principle upon which the theoretical conductibility, specific gravity, and expansion 

 are calculated, is similar to that followed with respect to hardness, for which, see Philoso- 

 phical Transactions, 1858. 



5* 



