thi three '3nc''M' Mif:!raT Act !s, 211 



tloning one general fo, rt of ..mi attending the mode of inve'^isjat'ion adopted by both, and 

 yet noticed by neither, naively, the lofs that many neutral falts uaJeigo during evaporation ; 

 a lofs, whofe difcovery is of confiderable importance, lot only to the prefent enquiry, but alfo 

 to the condudlof feveral manufa£lares, particularly to that of faitpetre, and hence noticed by 

 Mr. Lavoifier, 15 An. Cliem. 254. 



Other remarks and obfervations refpefting the experiments of Bergman, Wenzel, and 

 other chemifts, form a very eflemial and valuable part of the paper ; but the indifpenfable 

 attention to brevity, which the nature and obje<9: of a periodical work demands, will oblige me 

 to confine this abftra£l to the immediate ftru£ture and ufe of the tables. 



When alkalies or earths, combined with fixed air, are diflblved in acids, though far tht 

 greater part of the fixed air is expelled during the folution, yet fome portion of it is often 

 retained, and may, in fome degree, alter the fp. grav. of the folution ; this circumftance was not 

 recolledted by Mr. Kirwan till lately ; it was firfl: noticed by Mr. Cavendifli, Phil. Tranf. 

 1766, p. 172, and afterv/ards by Bergman, in his notes on SchefFer, § 51, but more explicitly 

 by Scheele, Chy. An. 1786, p. 13, and by Butini on Magnefia, p. 149. As to the ufe re- 

 fulting from refearches of this nature^ he remarks that it would be fuperfluous to attempt to 

 prove it at this day ; as the reeourfe which the moft eminent analyfts have been obliged to 

 have to it in particular inflances, fufficiently evinces it. " Inquiries of this kind (fays Mr. 

 " Fourcroy) are more difficult and delicate than thofe which have hitherto been, made on 

 ** falts; whatever requires a precife knowledge of quantities and proportions, prefents difficul- 

 *' ties fo great as often to appear infurmountable, yet without this knowledge no progrefs 

 '* can now be made in chemiftry," 10 An. Chy. 325 ; and according to Bergman, " Ufus 

 •* cognitx proportionis principiorum ingredientium egregius ell et mukifarius." i. Bergm. 

 137. chap. I. § I. 



The Experiments made for afcertaining the Changes of Denjtty in the Adds by Change of Tem^ 



peratureywere as follow : 



Vitriolic acid 1,8360 at temperature 60°, becomes 1,8292 at 70°; 1,8317 at65'';...,. 



1,8382 at 55''j«..i,8403 at 50°;....and 1,8403 at 49**.. — Hence we fee that vitriolic acid,, 

 whofe dcnfity at 60°, is 1,8360, lofes by ajcending and gains by defending o,ooc68 for 

 every degree of temperature between 60° and 70°, and 0,00043 nearly by each degree be- 

 tween 60° and 49°. . ^ 



Again, vitriolic acid 1,7005 at 60°, becomes 1,6969 at 70° ;.... 1,6983 at 65";....i,7037- 

 at 55°; and 1,7062 at 50". — Hence vitriolic acid, which at 60° is 1,7005, gains or lofes 

 0,00036 nearly for v^^ty degree between 60° and 70", and 0,00051 by every degree between^ 

 60' and 50°. 



Laftly, vitriolic acid 1,3888 at 60", becomes 1,3845 at 70° ;....!, 3866 at 65° ;.,.. 1,3898, 

 at 55°; and 1,3926 at 49" — Hence vitriolic acLd, which at 60"^ is 1,3888, gains or loies. 



0,00043, 



