472 



Frederick Guthrie on Eutexia. 



duction of dust of either of the nitrates, but begins when dust of 

 the solid eutectic alloy is introduced. The temperature there- 

 upon rises to 107°. This presumably proves that the alloy has 

 a crystalline form of its own, different from those of its two 

 constituents. Its composition was as follows, the lead being 

 weighed as sulphate. The two specimens were from sepa- 

 rate preparations, the only criterion of identity of composition 

 being identity of melting-point. 



(1) 2-8625 grams gave 1*2150 of sulphate of lead, or 1-3276 

 gram of nitrate of lead, or 46 '38 per cent, of nitrate of lead. 



(2) 2*3005 grams gave 0*9968 gram of sulphate of lead, 

 or 1*0892 gram of nitrate of lead, or 47*34 per cent. Taking 

 the mean, we have 



Eutectic alloy of 



Melting-point. 

 Nitre ....... 53*14 \ 9n?0 



Nitrate of lead .... 46*86 j /U ' ' 



§ 216. Nitre and Sulphate of Potassium. — Anhydrous 

 neutral sulphate of potassium dissolves in fused nitre, and sepa- 

 rates out therefrom as the fused mass cools in the form of a fine 

 powder. It is advantageous to allow the mass to lose heat 

 very slowly. As soon as the porcelain-like eutectic alloy 

 begins to be formed, the liquid is transferred into a fresh 

 crucible, and the solidification is continued. An alloy is thus 

 finally obtained of the constant melting-point of 300°. 



2*6625 grams gave 0*0836 gram sulphate of barium, corre- 

 sponding to 0*0627 gram sulphate of potassium, or 2*36 per 

 cent. 



Eutectic alloy of Melting-point. 



Nitre 97*64) _ 0O 



Sulphate of potassium . . 2*36 J U ' 

 § 217. Putting together the results of §§ 211-214, we have 

 the following table, in which the alloys are, like the cryohy- 

 drates of table § 88, arranged according to the lowness of the 

 melting-points. 



Table XLIII. 



Eutectic alloys with nitre. 



Name of salt. 



Temperature 

 of fusion. 



Per cent, 

 of salt. 



Per cent, 

 of nitre. 



Nitrate of lead 



o 

 207 

 251 



258 

 278 

 295 

 300 



4686 

 25-36 

 25-81 

 29-53 

 3-76 

 2-36 



53-14 

 74-64 

 74-19 

 70-47 

 96-24 

 97 64 



Nitrate of calcium 



Nitrate of strontium 



Nitrate of barium 



Cbromate of potassium . . . 

 Sulphate of potassium 



