Mixter — Formation of Trisodium Orthqphosphate, etc. 109 



small, as might be expected, since As 2 0., 3H 2 0=6'5 C only, while 

 P 2 5 , 3H 2 = 30-6 c . 



In conclusion it may be stated that the heat of formation of 

 trisodium antimonate from its elements is 346*4 C , and is derived 

 as follows : 



3]S T a 2 + 2Sb + 50 = 2Na 3 Sb0 4 + 393*3 C 



6Na + 30 = 3Na 2 + 299'4 C 



6^Ta + 2Sb + 80 = 2Na 3 Sb0 4 + 692'7 C 



3Na + 2Sb + 40 = Na Q SbO A + 346'4 C 



Bismuth Trioxide. 



Pulverized bismuth was burned in experiment 1. The tri- 

 oxide was made by heating pure basic bismuth nitrate in a 

 combustion tube to dull redness until acid fumes ceased to 

 come off. A weighed portion of the oxide was found not to 

 lose weight after fusion. The following are the experiments : 



Bismuth 



" unburned 



1 

 20-000 gr, 

 0-995 " 



" burned 



" trioxide . 



Sulphur _ 



19-005 " 

 1-000 " 



20-000 gr. 20-000 gr. 

 2-000 " 2-000 iC 

 Water equivalent of system 3,935 "4,256 "4,005 " 



Temperature interval.. .... 3-347° 3-445° 3-642° 



Heat observed 13,l70 c 14,662 c 14,586 c 



" of oxidation of sulphur — 5,27l c — 10,542 c — 10,542 c 



" " " " iron... — 48 c — 48 c — 48 c 



" " oxygen set free — 60 c — 28 c — 48 c 



7,791 c 4,044 c 3,948 c 



For 1 gram ... 410 c 202 c 197 c 



In calculating the heat of formation of bismuth trioxide it 

 makes no difference what sodium salt is formed in the fusion 

 since the same one results from the action of sodium peroxide 

 on both metallic bismuth and its trioxide. Moreover, assum- 

 ing that a different peroxide is formed than Bi 2 D does not 

 change the final result, since the heat effect of Na 2 + would 

 vary by 19,400 c in both of the calculations below. From the 

 mean of experiments 2 and 3 we have 



2Na 2 O g + xXa,0 + Bi 3 =: (Na 2 0)xBi 2 5 + .... 

 2Na 2 + 20 = 2Na 2 2 " + ..... 



92-8° 



38-8 



xNa 2 + Bi 2 3 + 20 = (Na. 2 0)xBi 2 5 + 



13T6 C 



