Its symbolic expression, to a numerical factor pres, is (Hbc) (Hbd) (Hcd) (bcd), and it is clearly of degree 6.
The summit C of the branch BCD occurs at a percentage exactly corresponding to the formula Hg 2 T1.
Then ABF = angle of elevation; EFB =quadrant angle; BCD=angle of sight; EBF=ABF - ABE; and since ABE = BCD, it also equals ABF - BCD.
Also, let angle ABC =7r - 0, angle BCD =ir - 4, angle between BC and AD = G.
BCD c is the solubility curve of phenol in water.
7 gives the freezing-point curve of mercury and thallium; here A and E are the melting-points of pure mercury and pure thallium, and the branches AB and ED do not cut each other, but cut an intermediate rounded branch BCD.