Notices of the Labours of Continental Chemists. 447 



a commonly received opinion, that allowing five of our English 

 feet to a geometrical pace, a thousand of these paces make an 

 Italian mile ;" and Fernel certainly used the Italian mile of 

 his day. On this the whole question seems to turn, but I 

 think I may confidently assert that no evidence can be brought 

 to show that the curious fiction which geometers of the six- 

 teenth century called a geometrical pace was even as long as 

 five English feet ; and certainly it was not longer. 



I remain, Gentlemen, yours faithfully, 

 University College, Oct. 26, 1841. A. De Morgan. 



LXVII. Notices of the Results of the Labours of Continental 

 Chemists. By Messrs. W. Francis and H. Croft. 

 [Continued from p. 285.] 

 On Succino-hyposulphuric Acid. 

 DY the action of anhydrous sulphuric acid on benzoic acid, 

 ■7"* Mitscherlich prepared his benzoesulphuric acid (benzoe- 

 hyposulphuric acid, Fehling). Mitscherlich's formula is 

 S 2 O 6 , C 14 H;° O 3 + H 2 O. Fehling gives the formula, ac- 

 cording to Liebig's theory of the constitution of organic acids, 

 as S 2 5 , C 14 H 8 O 3 + 2 H 2 O. Fehling has succeeded in 

 preparing a similar compound with succinic acid. He treated 

 succinic acid with the vapour of anhydrous sulphuric acid ; 

 it is absorbed in large quantities, and heat is evolved; a 

 brown elastic mass is formed, which must be allowed to stand 

 for twenty-four hours. The mass is then diluted with water, 

 and carbonate of baryta or lead added until the filtered solu- 

 tion gives no precipitate with chloride of barium. The filtered 

 solution is then precipitated by acetate of baryta or lead, and 

 from the edulcorated salt of lead the free acid may be prepared 

 by means of sulphuretted hydrogen. The solution evapo- 

 rated in vacuo gives small verrucose crystals, which cannot be 

 perfectly dried. The acid is soluble in water and alcohol. 

 These crystals, when heated with carbonate and nitrate of 

 potassa, gave 99*21§ sulphate of baryta; according to the for- 

 mula C 8 H 4 O 5 + S 2 O 5 + 8 H 2 O, the quantity would be 

 99-2£. The dry acid is probably C 8 H 4 O 5 + S 2 O 5 + 4 H 2 O. 

 From the composition of the salt of lead, it is probable that 

 the acid is quadribasic; 2 (C 4 H 4 O 3 + H 2 O) + 2 S O 3 

 = C 8 H 4 O 5 + S 2 O 5 + 4 H 2 O. By completely saturating 

 the acid with potash, a very deliquescent salt is obtained ; by 

 the addition of a little acid to its solution a salt is formed 

 which may be obtained in good crystals, and is not deliques- 

 cent ; it contains six atoms of water ; in vacuo it loses two 

 atoms. This salt with four atoms loses at 100° three atoms 



