290 Day and Shepherd — Lime-Silica Series of Minerals. 



of the solid phase, then to separate the mother liquor and, by 

 analysis of the two, to determine the composition of the solid 

 phase. In the case of mineral mixtures, the segregation of the 

 eutectic is, for laboratory experiments at least, very indefinite. 

 We have repeatedly examined different regions of a charge in 

 which the eutectic was known to separate, in the hope of find- 

 ing it segregated towards the middle of the charge, as commonly 

 happens with alloys, but in no case were we able to detect more 

 of the eutectic in one part of the charge than in another. It 

 is usually finely divided and intimately mixed with the primary 

 crystals. 



The properties of the pseudo-wollastonite which separates 

 along the branch BC are not quite identical with those of the 

 compound when prepared pure, from which it is evident that 

 a certain amount of silica must be taken up by it in solid solution. 

 The amount thus held in solution is certainly less than 2 per 

 cent, but its exact determination microscopically is very difficult 

 indeed. Furthermore, this pseudo-wollastonite when changed 

 to wollastonite still shows a slightly different optical character 

 from the pure material, showing that the solid solution appar- 

 ently continues after the inversion. For brevity, the pseudo- 

 wollastonite has been designated <x-CaSi0 3 , aud wollastonite 

 /8-CaSi0 3 in fig. 3. The branch of the liquidus CD was read- 

 ily determined, as well as the beginning of the branch DE. 

 It was not possible, however, to follow the branch DE beyond 

 57 per cent owing to the steepness of the curve, which rapidly 

 carries it out of the range of the accurate thermoelectric 

 methods. 



Table II. 



Curve of Melting Points. 



(Curve A B C D E F G, fig. 3.) 



Percentage of CaO 40 "0 



45-0 



48-2 



50-0 



52 



54 



55-5 



65 



675 



Component in 1457° 



1504° 



1512°* 



1505° 



1484° 



1435° 



15.16° 



2077° 



2015 



excess melts 1457 



1504 





1510 



1483 



1437 



1489 



2085 





1445 



1497 





1509 



1485 



1434 





2083 







1494 







1484 

 1483 



1482 

 1488 



1435 

 1435 

 1432 

 1432 

 1435 

 1433 

 1430 

 1429 









Mean 1453° 1500° 1512°* 1508° 1484° 1433° 1503° 2082°f 2015°f 



* Determined by Allen and White (loc. cit.). 

 f Determined with the Holborn-Kurlbaum optical pyrometer in the iridium furnace. 



