In spite of density is considered as one of the most important and characteristic properties which can be used only for confirming the structure of different types of glass, it is more liked to explain the glass structure in terms of the molar volüme than density as the former deals with the spatial distribution of the ions forming that structure. Such investigations of the density measurements and the molar volüme calculations aimed to throw some light on the structure of some sodiçum silicate and sodium boro-silicate glasses and possibly on the glass structure. The experimcntal results obtained showed that the values of the molar volüme decreased with the gradual increase of the soda content in sodium silicate glasses which may be due to formation of the more non bridging oxygens. Also, for sodium boro-silicate glasses the values of the molar volüme were found to decrease with increasing of the soda content and this can be explained according to the type of the introduced cations and their arrangements in the glassy netvvork structure.