This section is from the "Encyclopedia Of Practical Receipts And Processes" book, by William B. Dick. Also available from Amazon: Dick's encyclopedia of practical receipts and processes.
Degrees of Baum'e.
66. To Convert Degrees Baum'e into Specific Gravity. I. For liquids heavier than water. - Subtract the degree of Baum'e from 145, and divide into 145; the quotient is the specific gravity.
II. For liquids lighter than water.—Add the degree of Baum'e to 130, and divide it into 140; the quotient is the specific gravity.
67. To Convert Specific Gravity into Degrees Baum'e. I. For liquids heavier than water. - Divide the specific gravity into
145, and subtract from 145; the remainder is the degree of Baum'e.
II. For liquids lighter than water. - Divide the specific gravity into 140 and subtract 130 from the quotient; the remainder will be the degree of Baum'e.
68. Twaddell's Hydrometer. This Hydrometer is much used in the bleaching and dyeing establishments in Scotland, and some parts of England. According to this scale 0 is equal to 1000, or the specific gravity of distilled water, and every additional 5 degrees of specific gravity adds 1 degree,to Twaddell's scale. So that, in order to find the specific gravity corresponding to any degree of Twaddell's scale, multiply the degree by 5 and add 1000; thus, if this hydrometer shows 30°, 30 multiplied by 5 gives 150, and 1000 added makes 1150, the specific gravity. To find the degree of Twaddell corresponding to any specific gravity, deduct 1000 from the specific gravity, and divide the remainder by 5; the quotient will be the corresponding degree of Twaddell.
Thus, if it be required to find the degree of Twaddell corresponding to 1150 specific gravity, deduct 1000 from 1150, and divide the remainder, 150, by 5, and the quotient, 30, gives the degrees of Twaddell required. In this way the corresponding degrees of Twaddell and Baum'e can easily be found. Thus, 31 degrees of Baum6 are equivalent to a specific gravity of 1275; and this, according to the above rule, will give 55 degrees Twaddell. By reversing this process, Twaddell can as readily be reduced to Baum'e.