Frederick Guthrie on Euteocia. 471 



furnishing nitrates alloyable with nitre. The method of expe- 

 riment was precisely as before, the nitrates having been 

 rendered anhydrous before they were added to the fused nitre. 

 The bases were all separated and weighed as carbonates. 



The eutectic alloy of nitre with nitrate of calcium has a 

 melting-point of 251°. Of this, 1-8300 gram gave 0*2830 

 carbonate, or 0*4641 gram nitrate of calcium. This corre- 

 sponds to 25*36 per cent. 



§ 213. The eutectic alloy of nitre with nitrate of strontium 

 has a melting-point of 258°. Of this, 1*9490 gram gave 

 0*3498 gram carbonate, or 0*5031 gram nitrate. This corre- 

 sponds to 25*81 per cent. 



§ 214. The eutectic alloy of nitre with nitrate of barium 

 melts at 278°*5. Of this, 2*6100 grams gave 0*5860 gram 

 carbonate, or 0*7773 gram nitrate of barium. This corre- 

 sponds with 29*53 per cent. 

 Eutectic alloys of : — 



Melting-point. 



Nitre 74*641 251 o 



Nitrate of calcium . . . 25*36 j 

 Nitre ....... 74*19) 25 g 



Nitrate of strontium . . 25*81 J 



Nitre 70*47 \ 97RO 



Nitrate of barium . . . 29*53 J Z '° 

 In this group strontium holds its accustomed intermediate 

 place between calcium and barium ; but, both in regard to 

 the melting-point and to the composition of its eutectic alloy, 

 it more closely resembles the former than the latter. 



§ 215. Nitre and Nitrate of Lead. — The eutectic alloy formed 

 by these salts is of great interest, not only because the lead 

 element, like the chromate of potassium and the nitrates of 

 barium and strontium, cannot be fused alone without decom- 

 position, but because it, the alloy, has a remarkably low melting- 

 point, and because either constituent in excess of its quantity 

 in the eutectic alloy raises the melting-point in a manner easy 

 to be followed. To the fused nitre the dry nitrate of lead is 

 added, and on cooling one or other separates out in crystals 

 easy to distinguish. More of the salt which is in fusion is 

 added, until this is in its turn the one which separates on cool- 

 ing. The same process having been repeated three or four 

 times, the whole is allowed to lose heat as before. The tem- 

 perature soon settles at 207° C, and thereupon the liquid 

 begins to solidify as a beautiful white opaque porcelain-like 

 mass, startlingly like the cryohydrates. The temperature 

 may at first sink to 203° C; and when in this condition of 

 supersaturation, solidification is not to be induced by the intro- 



