Crafts et al. 



4 — 



Water in Plants 



Table 1. — Some thermal properties of water and several elements and compounds: 



Substances 



Heat capacity per gram 

 formula weight 



Calories Temp. ° C. 



Heat of fusion 

 calories per gram 



Calories Temp. ° C. 



Heat of vaporization 

 calories per gram 



Calories Temp. ° C. 



Hydrogen 3.4 



Oxygen 3.5 



Nitrogen 3.5 



Sulfur 5.3 



Water, liquid 18.1 



Water, solid 9.1 



Carbon dioxide 8.7 



Ammonia 8.8 



Hydrogen sulfide .... 4.6 10 



Sulfur dioxide 15.4 10 



15.0 



6.1 



10.4 



80.0 



45.4 

 108.0 



—219.0 



—210.0 



119.0 







— 56.2 



— 75.0 



108.0 

 50.9 

 47.6 



66.3 

 539.0 



87.0 

 327.0 

 132.0 



95.0 



—252.8 



—182.9 



—195.5 



444.6 



100.0 



— 60.0 



— 33.4 



— 61.4 



— 10.0 



Table 2. — Physical properties of water and some other common liquids: — 



Substances 



Surface tension 

 Dynes/cm. Temp. 



Internal pressure 

 Atmospheres 



Dielectric constant 

 E Temp. ° C. 



Water 75.6 



Mercury 47.6 20 



Carbon disulfide 35.3 



Benzene 31.6 



Carbon tetrachloride 29.0 



Hexane 20.5 



Ethyl alcohol 24.0 



16,400 

 13,050 

 5,400 

 4,050 

 3,640 

 2,020 

 7,200 



81.000 



17 



be around — 100° C. to — 150° C. In comparison HgS, containing sulfur 

 that boils at 444° C, is a gas boiling around — 61° C. 



H 

 H-6- 



H 

 -6-H 



V 



Fig. 1. — Trihydrol molecule as pictured by Suth- 

 erland (1900). 



Other anomalous properties of water include its minimum specific heat 

 at 37.5° C, its maximum density at 4.0° C, and its great expansion upon 

 solidification. This latter property has played an important part in all at- 

 tempted explanations of the structure of water. 



Early Theories: — The earliest concepts of the liquid structure of water pictured 

 it as composed of spheroid molecules, heterogeneously arranged, and having the un- 

 ordered motion of a very dense gas. As early as 1884, however, Whiting visualized 

 liquid water as a solution of ice particles and Raoult (1885) pictured association of 

 water molecules into groups of four. Vernon (1891) explained the maximum density 

 of water by association of the molecules from (H20)2 above 4° C. to (H20)4 below 

 that temperature. In 1892 R5ntgen independently proposed that liquid water is made 

 up of a saturated solution of ice in some other form of water. He pictured ice mole- 

 cules as complex, but less dense than water; when ice melts the volume is decreased. 



