THE ANALYST. 189 NOTE ON THE SPECIFIC GRAVITY OF LIQUIDS. BY L. SIEBOLD, F.C.S. While tlie great usefulness of the liydrometer for the rapid determination of tlie specific gravity of all lrinds of clear liqnids is universally recognized, there appears to be aiiytliing but unanimity of opinion as to the value of this instrument as an indicator of the specific gravity of mixtures owing part of their weiglit to tlie presence of uii- dissolved or suspended matter.I have therefore made a number of experiments wit11 tlie object of deciding whetlier or not the indications of the hydrometer may be depended upon in tlie case of mixtures containing insoluble powders, oils, resins, kc., uiiiformly suspended. The results were as follows :- Xixturcs of Przcipitated Chalk, Mucilnge of Acacia, Syrup altd Watey- Specific gravity Specific gravity by hydrometer. by balance.No. 1. . . . . . . . . 1.106 .. 1.1066 .. 2. . . . . . . . . 1.070 .. 1.0710 Uixcfures of X q n e s i a , N u c i l a g e aiid Jb-uter- Specific grauity Specific gravity by hydrometer. by balance, No. 1. . . . . . . . . 1.039 .. 1.0598 ,, 2. . . . . . . . . 1.036 .. 1.0359 DIixture of Precipitated Chalk and W’ater only- Specific gravity Speciflc gravity by hydrometer.by balance. 1.037 .. 1.0396 Tlie difference in this case arose from the fact that it was impossible to read off tlie specific gravity quickly enough, for in the absence of the mucilage or any other binding substance, the chalk began to subside immediately after shaking, thus causing a continual decrease in the specific gravity, Mixtures containing subnitrate of bismuth, heavy spar and other mineral powders, each suspended by mucilage, were tested in the same manner and likewise gave con- cqrdant results.Emulsions of Oil of Almonds, Giiin Acncia, and V a t u - Specific gravity Specific gravity by hydrometer. by balance. No. 1. . . . . . . . . 1.010 .. 1.0110 .. 2. . . . .. . . . 1.007 .. 1.0070 Emulsion of Coliaiba, Xucilnge and Water- Specific gravity Specific gravity by hydrometer. by balance. 1.014 a . 1.0144 * The physical properties of the benzoliiie examined by me are very different from those attributed to the liquid by Wiederhold, who on fractionally distilling benzoline of *716 sp. gr., which commenced to boil at GOo, obtained- 48.6 per cent.of -70 sp. gr., boiling at loo0. 45.7 ,, -73 ) ) ,, 200”. 6.7 ,, ‘80 .. I . above 2003.190 THE ANALYST. VCZ r i m s sn Iitples n f illill; - Spscilic gravity Specific gravity by hydrometer. by babncc. So. 1. . . . . . . . . 1.030 .. 1-0305 .. 2. . . . . . . . . 1.028 .. 1.0278 , , 3 . . . . . . . . . 1.032 .. 1.0316 ,, 4. . . . . . . . . 1.029 * . 1.0300 Spxific grarity by belance.1.1670 Tlie last determination was made in order to see wlietlier tlic gred viscosity of thc liquid would have aiiy notable effect on tha iiidications of tlie hydrometer. All the determinations were made at 62Q F. The set of liydrometers used consisted of instruments specially made for very short ranges of specific gravities, the correctness of which I had frequently checked in previous detcminations. The foregoing experiments prove that carefully made hydrometers aflord reliable iiidications of tlie specific gravities of liquids, no matter whether their gravity is due t o dissolved or suspended substances.