produced by the mutual Reaction of Solid Substances. 297 



Six minutes were required to reach the lowest point; and 

 during the next five minutes there was a gain of but o, 5. 

 Stirring was stopped at the end of eleven minutes. 



Lowest attainable Temperature. — In addition to Guthrie's 

 discoveries already mentioned, he found that when two salts 

 were used with ice the minimum temperature was unlike that 

 of either alone, each exercising an influence over the other. 



Most of my experiments with the calorimeter were made 

 for the purpose of discovering whether or not the lowest at- 

 tainable temperature of a given salt when mixed with ice is 

 the same if that salt is produced in a freezing-mixture of two 

 salts, also if it is independent of the initial temperature and 

 the proportions used. 



The hydrated sulphate and carbonate of sodium were each 

 mixed with various nitrates, whereby nitrate of sodium was 

 produced and a sulphate or carbonate, usually an insoluble 

 compound, which I thought could not influence the result. 



The lowest attainable temperature of sodium nitrate with 

 ice is -17° C. 



The following results were obtained with metals whose 

 carbonates 

 pounds : — 



are without doubt anhydrous insoluble com- 



withNa 2 CO 3 .10H 2 O 



Initial 



Lowest 





temp. 

 d 19°C. 



temp. 

 -17° 



Loss. 

 36° 







-17 



17 



21-3 



-13-7* 



35 



- 1 



-17 



16 



14 



-18 



32 



- 4 



-18 



14 



16-5 



-18 



34-5 



- 2 



-15 1 



13 



Pb(N0 3 ) 2 

 Ba(N0 3 ) 2 

 A1 2 (N0 3 ) 6 .18H 2 

 Cu(N0 3 ) 2 .6H 2 



With the nitrates of zinc, manganese, iron, and chromium 

 the results were not so free from modifying influences as I 

 had anticipated, basic carbonates being formed not wholly 

 insoluble at low temperatures. 



The interesting fact was thus revealed that ferric carbonate 

 or basic carbonate exists in the liquid form at a low tempera- 

 ture, say —20° 0. The colour is a deep red ; and, as the mix- 

 ture gradually warms, C0 2 is rapidly given off, causing the 

 contents of the beaker, which was not at first more than half- 

 filled, to overflow and insoluble Fe 2 3 to be deposited. 



* An insufficient quantity was taken, 

 t Liquefaction proceeded very slowly. 



Phil. Mag. S. 5. Vol. 12. No. 75. Oct. 1881. Z 



