28 GENERAL BIOCHEMISTRY 



the origin of life as we know it without an abunchtnce of water. Even 

 though another liquid might be proposed as a replacement, the 

 unusual properties of water make it a unicpie basis for the life of the 

 eartli. 



A complete understanding of the unusual properties of water is not 

 yet available. Yet some ideas have been proposed to account for the 

 behavior of this strange substance. As usually represented by chemists, 

 water has the formula HgO, corresponding to a formida weight of 18. 

 However, this low value would indicate a low boiling point for the 

 substance since there is a correlation between molecular weight and 

 boiling point in a series of similar compounds. This comparison of 

 water in Table 2-1 with the members of two of its chemically related 



TABLE 2-1. The Boiling Points of Water and Certain Related Compounds 



Formula Boiling Formula Boiling 



Substance Weight Point, °C. Substance Weight Point, °C. 



families illustrates its unique position. The boiling point of water 

 compared to the boiling points of the other members of the inorganic 

 group at the left suggests that perhaps the individual water units are 

 associated in the liquid state. Otherwise water ought to boil below 

 ~60°C., perhaps about ~65°C. If association gives rise to the high 

 boiling point, extrapolation indicates that the aggregates of water 

 might have average relative weights of about 200. 



When compared with the alcohols the position of water is not quite 

 so extreme. Yet water is anomalous even here. Moreover, comparison 

 of the alcohols with the inorganic substances suggests that even the 

 alcohols may be somewhat associated in the liquid state. Unfortunately 

 no direct determination of molecular weight in pure liquids has been 

 devised, so these speculations have not been verified. Still there are 

 a few experimental indications that liquid water consists of aggregates 

 of subunits. These aggregates are presumed to dissociate rapidly and 

 reversibly, leading to a dynamic system containing structures of various 

 sizes. 



Existence of aggregates in water implies the presence of strong inter- 



