Specific gravity, Determination

It is rarely that any greater degree of accuracy than that attained in the above methods is required. If, however, scientific accuracy is necessary in specific gravity determinations, the usual standard of comparison, at whatever temperature the determination may be made, is water at its maximum density temperature, namely 4°. If no correction is made for the weight of the air contained in the bottle or tube, accuracy to the fourth place of decimals is ensured by reducing the observed weighings to vacuum weighings. This can be done by the equation—... 

The weight in air/weight in water method is one of the traditional methods of specific gravity determination. Selected sample units are first weighed in air and then the same unit is re-weighed suspended in water. Typically a computerized apparatus is used, such as that described by Tai et al. (1985). A potato hydrometer which is used with a fixed weight of potatoes may also be used for this purpose. 

The solubility of ammonium iodide 6 in water is very great. At —27 5°, the cryohydric temp., water dissolves 55 per cent, of the salt, and at 15°, 62 5 per cent. A contraction occurs when this salt dissolves in water. Thus, H. Schiff and U. Monsacchi 7 calculate from the specific gravity determinations of W. H. Perkin and W. W. J. Nicol ... 

For the specific gravity determined in a pycnometer with mercury, a series of diminishing figures has been established ... 

Stull, J. W., Taylor, R. R. and Ghlander, A. M. 1965. Gradient balance method for specific gravity determination in milk. J. Dairy Sci. 48, 1019-1022. 

N, Shaking Density. It is a density of an explosive submitted in bulk after it undergoes shaking as prescribed by the BurMines Test (Ref 4, p 24). See under Density and Specific Gravity Determinations of Solids, item w)... 

There are also other methods of measurement (Ref 13, pp 890-92 Ref 23, Method D1070) Density and Specific Gravity Determinations of Solids... 

The procedure rs more rapid if the West-phal Balance is used. This device is described as item b, under Density and Specific Gravity Determinations of Liquid . For detn of sp gr of solids, the plummet is replaced by the sample (in the form of a lump), suspended by a non-corrosive wire... 

Note 3 The above described method is not as accurate as the procedure described as item c, under "Density and Specific Gravity Determinations for Liquids", but it seems that this "precision" is sufficient in testing proplnts d) Density in Vacuo Method. The US military procedures, described in Ref 21 as Method 202-2, for detg density of expls and proplnts in pellet form is as follows ... 

Specific Gravity Determine by any reliable method (see General Provisions). 

Solubility in Alcohol Determine as directed under Solubility in Alcohol, Appendix VI. One milliliter of sample dissolves in 1 mL of 90% alcohol, often with turbidity, and remains in solution on further addition of alcohol to a total of 10 mL. Specific Gravity Determine by any reliable method (see General Provisions). 

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