Correlation Between Density and Ash,Organic,and Water Contents of Calcified Tissues. ∗

There are two reliable methods for determining the density of minute particles of calcified tissues, namely (a) comparison of the refractive index with that of a liquid of known density, 1 and (b) flotation of the particle in a liquid of known density. 1 , 2 , 3 Knowing the density of the particle, and the relationship of density to the ash content, one then could roughly estimate the ash in particles of bone or tooth substance too small to weigh accurately. Figure 1 shows this correlation between ash and density. Table I contains data for constructing this chart and similar ones for estimation of the organic and water contents.

Methods. The density of 145 samples of dentin, normal and in varying degrees of decalcification, and 10 samples of beef bone was determined while wet. 4 Ash, organic and water determinations were then made on each sample. 5 The data were treated by the method of least squares 6 and the necessary values (a,b) for construction of the charts recorded in Table I. It must be remembered that “a” is the y intercept at x 0.