100 Prof. Louis Henry on the Polymerization 



Thus, when crystalline plumbous hydrate, 3PbO . H 2 0, loses 

 its last molecule of water under the action of heat, it * is not 

 PbO which is formed, but at least (3PbO) 2 . When H 2 Si 8 ]7 

 becomes the anhydride, we do not get Si0 2 , but at least 

 (Si 8 16 ) 2 . For a similar reason metaphosphoric acid cannot 

 be HP0 3 , but is at least (HP0 3 ) 2 , since it is formed by de- 

 hydration of H 4 P 2 7 . 



The structure of these oxyhydroxides leads to the con- 

 clusion that they are, in effect, fragments of the normal 

 hydroxides, R^OH)^, linked together by atoms of oxygen, 

 thus : — 



H,P0 4 . . PO(OH) 3 

 H 4 P 2 7 . . PO(OH) 2 



l 

 



PO(OH) 2 



H 2 Pb0 2 . . Pb(OH) 2 

 H 2 Pb 3 4 . . Pb(OH) 



6 



I 

 Pb 



6 



Pb(OH) 



The fact of the polymerization of an oxide at the moment 

 of dehydration of the corresponding hydroxide, is also con- 

 firmed experimentally in certain cases, thus : — The methylic 

 and ethylic arsenites (CH 3 ) 3 As0 3 and (C 2 H 5 ) 3 As0 3 are decom- 

 posed by w r ater, and give, not arsenious acid, H 3 As0 3 , but the 

 solid anhydride, which is, even in the state of vapour, a 

 polymer represented by As 4 6 . 



The same thing also holds good w r ith methylene oxide. Its 

 chloracetate, CH 2 C1 . OAc (Henry, Bull. Acad. Belg. xxxv. 

 p. 717), its diacetate, CH 2 (OAc) 2 , and the compounds ob- 

 tained by Friedel (Compt. Rend, lxxxv. p. 2471) are also 

 decomposed by water, yielding, not the hydroxide CH 2 (OH) 2 , 

 but the solid polymerized oxide (CH 2 : 0)*. 



The metallic oxides can be obtained from their different 

 salts by various reactions. These general methods furnish a 

 number of facts which tend to prove the polymeric nature of 

 these compounds, We will examine successively in this con- 

 nection the various classes of salts, such as carbonates, sul- 

 phates, &c. 



Carbonates. — As a general rule most carbonates are de- 

 composed by heat, leaving an oxide. For this reason these 

 salts are perfectly assimilable to the hydroxides, and we may 

 therefore confirm by their help the results previously arrived 

 at. The chief difference is the degree of heat required. 



It is important, from our point of view, to show that de- 



