}ranchester Memoirs, Vol. Iv. (191 1 j, No. 10. 9 



(i) Metaboric acid is probably a definite compound, 

 or hydrate of boric anhydride. 



(2) No clear evidence can be found for the existence 

 of any acid containing less water than metaboric acid. 



(3) Only orthoboric acid can exist in solution, under 

 which conditions it is present in simple molecules. 



(4) Metaboric acid cannot be regarded as an equi- 

 molecular mixture of orthoboric acid and boric anhydride. 



(5) Fused mixtures of orthoboric acid and boric 

 anhydride, in which the molecular ratio of the latter to 

 the former compound exceeds 41, can exist in a vitreous 

 metastable and a crystalline stable form. 



Boron and aluminium being members of the same 

 group of elements, analogies may be expected between 

 them, and, as in the case of the latter element, a very 

 complicated series of hydrated oxides are believed to 

 exist, the same may be true for boron. This view would 

 help to explain many of the experiments described in 

 this paper, the ortho variety being the only definite acid 

 of boron. 



The University, Manchester. 



