2 
beaume's hydrometers. 
generally in use, and their scales subject to the greatest variations. 
Tables of comparison have been made by Delezannes, Francoeur, 
Bohnenberger, Gilpin, Dr. Ure, Nicholson, Vauquelin et Darcet, 
and others, but they are all formed from the original scale of 
Beaume by calculation, or obtained from direct experiment by 
taking the sp. gr. of liquids in which the hydrometer sinks to 
various degrees. 
No scale formed from experiments can be depended upon for 
accuracy, as a proof of which it is impossible to find two scales 
so formed agreeing, the error often affecting the first decimal 
place. 
The basis upon which Beaume formed his scale was very un- 
fortunately chosen, and gave rise, at an early period, to changes 
that have completely modified even the theory of his instrument ; 
he obtained the zero for his scale for light liquids, or pese esprit, 
by immersion in water containing ten per cent, of salt in solution, 
and the point to which it sunk in pure water he made 10°, divid- 
ing the stem into like intervals he obtained the 20°, 30°, &c, the 
intermediate degrees by subdivision. The hydrometer for heavy 
liquids of pese acide was differently adjusted. Water gave 0°, and 
the point to which it sunk in a solution containing fifteen per 
cent, of salt, he marked as 15°, the interval doubled gave the 30°, 
the next the 45°, and so on. Now it is evident that if an error is 
made in obtaining the first interval, it becomes multiplied in ex- 
tending the scale, and even with the greatest care it would be im- 
possible to obtain two instruments graduated precisely alike; the 
only reliable plan is to subdivide points obtained at the extremes 
of the scale, and this has been the practice with the makers since 
an early period.* 
In an article byFrancoeur entitled " Areometre," and published 
in the Dictionnaire Technologe, at Paris, in 1822, the author says, 
in speaking of the method of graduation, " This kind of fault is so 
serious, that the workmen, knowing from the experiments of Guy- 
ton that concentrated sulphuric acid should mark 66 B., commonly 
* Beaume also pointed out another 11 Pese Sel j" he made several saline 
solutions — each giving its own degree — 5 parts of salt in 95 parts of water 
gave 5°, 10 parts of salt and 90 parts of water gave 10°, &c. (Dictionnaire 
Technologe.") This tended to increase the confusion, though it probably 
never came into general use, as the scale could not be extended beyond 25°. 
