102 



lime, jii'd'cr lo call tliciii li(|ui(ls of lii<^ii x'iscosily; slill 

 olliers, c'onsideriiij;' the met hod of ol)taiiiin^' glasses and 

 llieir amorplioiis iialure, insist on callini;' llicm sni)or-cool('d 

 li(|nids. Detinini*- a state by its relation to temperatnre (as 

 illnslraled in Fi.n'. 1), !)>■ the consistency of the matei'ial 

 and l)y the arrani-ement of the constituent jjarticles, we 

 shall distinguish four states of matter: vitreous, crystal- 

 line, liquid and gas. 



This classification of the states requires a revision 

 of the classification of the transitions from one state to 

 another. The following list gives the various ])ossil)ilities. 

 (We coined a few names, when such wei-e lacking; they are 

 indicated by (inotation marks.) 



C^HANOEs OF State 



the vitreous to the crystalline state: 

 the crystalline to the vitreous state: 

 the vitreous to the liquid state : 

 the liquid to the vitreous state: 

 the vitreous to the gas state: 

 the gas to the vitreous state: 

 the crystalline to the liquid state: 

 the liquid to the crystalline state: 

 the crystalline to the gas state: 

 the gas to the crystalline state: 

 the liquid to the gas state: 

 the gas to the liquid state: 



Devitrification 



(Tmpossilile) 

 ' ' Vitromelting' ' 



Vitrification 

 ' ' Vitrosubliniation ' ' 

 ' * Gasovitrification ' ' 



:Nrelting 



Crystallization 



Sublimation 

 ' ' Gasocrystallization ' 



Vaporization 



Liquefaction 



The liquid state can be maintained also at temperatures 

 below the f 7'eezing point ; one then obtains, besides the 

 four states just described, a supernumerary one (called 

 state in a broader sense), the supercooled state. 



Of these five states there are only three which protoplasm 

 can take at low temperatures, the crystalline, the vitreous 

 and the supercooled; the liquid state obtains at ordinary 

 temperatures and the gas state is unknown in protoplasmic 

 substances. As to the changes of state, the most important 

 for the biologist are: crystallization (that is, freezing), 

 melting, vitrification, devitrification and "vitromelting." 

 Consequently we shall divide this work into the following 

 chaptei's: I. Freezing, the Frozen State and ^Melting; TI. 

 Sni)ercooling and the Supercooled State ; IIT. Vitrification, 



