70 



THERMO-CHEMISTRY. 



(90) HEAT EVOLVED OR ABSORBED IN CHEMICAL AND PHYSICAL 

 ACTIONS. 



The symbols in the following tables express the atomic weights 

 <f the elements taken in grams, and the heat evolved or absorbed 

 ( - ) is expressed in " large " calorics (kilogram-degrees). Aq means 

 that an indefinite quantity of water is present, s that the substance 

 is solid, / li juid, and g gaseous. 



(91) ALLOTROPIO CHANGES OF THE ELEMENTS (see 90). 



Oxygen into ozone, 30 2 = 20 3 - 29'6 



Common into insoluble sulphur S. at 1 8 C 



Amorphous insoluble sulphur into amorphous soluble '08 



Amorphous soluble sulphur into octohedral S a - O'OS 



Plastic into octohedral sulphur S y = S a ... 0*4 



Prismatic into octohedral sulphur S^ S a '08 



Vitreous into metallic selenium Se 56 



White into red crystallised phosphorus P 19 '2 



White into red amorphous phosphorus P. at 9 C 207 



Wood charcoal into diamond C 3 



Amorphous into crystallised silicon Si 8 1 



Gold ppd. from bromide into condition of that ppd. fr. 



chloride Au 3 '2 



Iron at 700* C - 0'28 



]ronat!000C - 0'34 



(92) HEAT OF SOLUTION IN WATER OF 22 3 LITRES OF GASES 

 (see 90). 



Chlorine C1 2 3 Hydrogen Nitrate HNO... 14'4 



Bromine Br 2 8'3 Sulphur dioxide S0 2 ...... 77 



Hydrogen Chloride HC1... 17 '4 ,, trioxide SO 3 246 



,, Bromide HBr... 20 Chlorine monoxide C1 2 0... 9'4 



Iodide HI 19'4 Boron trichloride BC1 3 ... 703 



Sulphide H 2 S... 475 Silicon tetrafluoride SiF 4 . . 22 3 



AmmoniaNH 3 8'8 Boron trinuoride BF 3 24'5 



Nitrogen TrioxideN 2 3 ... 138 Carbon dioxide C0 2 5 '6 



,, pentoxide N 2 5 . 29'8 Hydrogen cyanide HCN... 6'1 



