THE HAUMK 1 1 V DKO-AriOTKHS. (55 



Tlic only tliiiiji to be done is to coirec^t tin- iiiiieciuacies aiul estahli.sli b.v some coiiiiieteiit 

 aiitlioiity ail aiitliorized and acceiited standard of values for tlie Banni(5 scales. 



Hauint''s inetliods were lirst described in I'Arnnt Ci>urcur towards tlie close of ITtlS. Tliey 

 have been repeated in the several editions of liis Rienicnts de Pharniacie. In the eighth edition 

 of this work, published in Paris in 17!tT, he st;ites tliat he constructed his instruments in this way = 



(1) For the hi/di-onteter far l!<iiiiils licariir thiiii water he prepared a solution of salt (u)ntaiiiing 

 tifteen (15) parts of salt by weight in eij;lity-five (85) parts of watei- by weight. He describes the 

 salt as "very pure'' and "very dry," and states that the experiments should be made in a cellar 

 iu which the temperature is 10° Keauniur, equivalent to 12.0° Centigrade and to 54.5° Fahrenheit. 

 The zero ou the scale indicate.s the point to which the instrument sinks in distilled water (at the 

 temperature above stated), the 15 mark the point to which it sinks in the 15 percent, salt solution. 

 Witli a pair of dividers the space between "0" and " 15" is divided into fifteen equal i)arts, and 

 degrees of the same size are coutiiiued above " 15." 



Baum^'s idea was that each additional degree ou this scale would indicate one additional per 

 cent, of salt, which of course is not quite correct, but the directions given are sufficiently simi)le to 

 enable any person to reproduce the instrunieut. 



(2) For the hydrometer for liquids tighter thati ia(ter he uses a 1(1 per cent, solution of salt 

 prepared in the same way, and hy means of it fixes the zero point on the hydrometer. He uses 

 distilled water for the " 10" point, and obtains a scale as iu the case of the other instrument, but 

 running in the opposite dii'ection. 



With so .simple and direct a statement as this it is remarkable that it has been possible to get 

 .so far away from the true Baume scales. In looking over the literature of the subject 1 find that 

 these discrepancies have arisen fiom various causes — either neglect to follow Baum^'s directions, 

 or a deliberate attempt to improve the scales. 



(a) Baume conveys the idea that each degree represents 1 per cent, of salt, and he even sug- 

 gests that in order to obviate errors due to irregularities in the stem of the instrument, a series 

 of solutions may be prepared, the first containing 1 per cent, of salt and 99 jier cent, of water, the 

 second 2 per cent, of salt and 98 per cent, of water, and so on, and that the degrees 1, 2, &c., can 

 l)e marked by the use of these solutions. 



(b) Acting still further on this suggestion of Baume, many instrument makers gave up pre- 

 paring the 15 per cent, salt solution altogether for fixing the " 15" mark, using instead the 10 per 

 cent, solution and fixing by it the " 10" mark, thus making one solution answer for both instru- 

 ments. 



(c) It was found at an early day that oil of vitriol generally stood at about 66 on the Baume 

 instrument; so many instrument makers fixed the 66 mark by immersing the instrument in oil of 

 vitriol. As a matter of fact oil of vitriol is a variable substance. It never contains 100 per cent, 

 of sulphuric acid^usually only from 92 to 96 per cent. It consequently has a variable specific 

 gravity, and its use for the 66° mark introduces varying errors. 



SCALKS FOR LIQUIDS HEAVIER THAN WATER. 



I submit herewith a table — -'Table No. I" — containing twenty-three different scales of values 

 for the degrees on the instrument for liquids heavier than water, and another table — "Table No. 

 II" — containing the eleven scales for liipiids lighter than water. 



METHODS I:MFL0YED IN SECTRINCi THE SCALES GIVEN IN TABLE I. 



(1) Delezennes. 66o=1.8922. The mark for 10° was found by a 10 per cent, salt solution at 

 10° E. (Wagner Jahresb., 1869, vol. 15, 236.) This scale appears in Journal de Pliys., vol. 

 94, 204; Bache & McCulloh, 1848, 116: Dingler's Polyt. Journal, 1865, 2 vol., 176, 4.55; Handwor- 

 terbuch der Chemie, 1859, vol. 2, 1, 179; Knapp, Chem. Tech. 



(2) Ziurek. 66o=1.8.50. No method given. This scale appeai-s in Technologische Tabellen, 

 1863, 35. 



(3) D'Arcet. 66° = 1.84'.i (calculated). The point 66° B. was obtained in sulphuric acid of spe- 

 cific gravity 1.830, but it is assumed that it is not pure hydrate, but contains about 6 to 7 per cent. 



S. Mis. 69 9 



