Hydrometers

Because of their widespread use for simple process control, hydrometers are frequently calibrated, not in specific gravity, but in some units related to it, which bear (or bore at one time) some relationship to the concentration being so measured. 

Density is generally measured at 15°C using a hydrometer in accordance with the NF T 60-101 method it is expressed in kg/1 with an error of 0.0002 to 0.0005 according to which category of hydrometer is utilized. However, in practice only three decimal places are usually retained. 

Density Density and specific gravity NFT 60-101 ISO 3675 ASTM D 1298 Hydrometer... 

The API gravity of water is 10°. A light crude oil would have an API gravity of 40°, while a heavy crude would have an API gravity of less than 20°. In the field, the API gravity is readily measured using a calibrated hydrometer. 

The oil density at surface is readily measured by placing a sample in a cylindrical flask and using a graduated hydrometer. The API gravity of a crude sample will be affected by temperature because the thermal expansion of hydrocarbon liquids is significant, especially for more volatile oils. It is therefore important to record the temperature at... 

The density of the electrolyte, measured by a hydrometer, forms a useful indicator of the state of charge or discharge of the battery. 

Hydrometers. Various hydrometers and the relation between the various scales. 

Alcoholometer. This hydrometer is used in determining the density of aqueous ethyl alcohol solutions the reading in degrees is numerically the same as the percentage of alcohol by volume. The scale known as Tralle gives the percentage by volume. Wine and Must hydrometer relations are given below. 

Ammoniameter. This hydrometer, employed in finding the density of aqueous ammonia solutions, has a scale graduated in equal divisions from 0° to 40°. To convert the reading to specific gravity multiply by 3 and subtract the resulting number from 1000. 

Beck s Hydrometer. This hydrometer is graduated to show a reading of 0° in pure water and a reading of 30° in a solution with a specific gravity of 0.850, with equal scale divisions above and below these two points. 

Cartier s Hydrometer. This hydrometer shows a reading of 22° when immersed in a solution having a density of 22° Baume but the scale divisions are smaller than on the Baume hydrometer in the ratio of 16 Cartier to 15 Baume. 

Fatty Oil Hydrometer. The graduations on this hydrometer are in specific gravity within the range 0.908 to 0.938. The letters on the scale correspond to the specific gravity of the various common oils as follows R, rape O, olive A, almond S, sesame HL, hoof oil HP, hemp C, cotton seed L, linseed. See also Oleometer below. 

Lactometers. These hydrometers are used in determining the density of milk. The various scales in common use are the following ... 

Oleometer. A hydrometer for determining the density of vegetable and sperm oils with a scale from 50° to 0° corresponding to specific gravities from 0.870 to 0.970. See also Fatty Oil Hydrometer above. 

Brix hydrometer is graduated so that the number of degrees is identical with the percentage by weight of cane sugar and is used at the temperature indicated on the hydrometer. 

Balling s saccharometer is used in Europe and is practically identical with the Brix hydrometer. 

See also below under Wine and Must Hydrometer. 

Sprayometer (Parrot and Stewart). This hydrometer which is used in determining the density of lime sulfur solutions has two scales one scale is graduated from 0° to 38° Baume and the other scale is from 1.000 to 1.350 specific gravity. 

Twaddell Hydrometer. This hydrometer, which is used only for liquids heavier than water, has a scale such that when the reading is multiplied by 5 and added to 1000 the resulting number is the specific gravity with reference to water as 1000. To convert specific gravity at 60°/60°F to Twaddell degrees, take the decimal portion of the specific gravity value and multiply it by 200 thus a specific gravity of 1.032 = 0.032 X 200 = 6.4° Tw. See also special table for conversion to density and Baume scale. 

Wine and Must Hydrometer. This instrument has three scales. One scale shows readings of 0° to 15° Brix for sugar (see Brix Hydrometer above) another scale from 0° to 15° Tralle is used for sweet wines to indicate the percentage of alcohol by volume and a third scale from 0° to 20° Tralle is used for tart wines to indicate the percentage of alcohol by volume. 

This table gives the relation between density (c.g.s.) and degrees on the Baume and Twaddell scales. The Twaddell scale is never used for densities less than unity. See also Sec. 2.1.2.1, Hydrometers. 

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