Chemistry and Physics. 433 



solidifying at — 88°, the results were similar. In like manner 

 potassium hydroxide remains unacted on below — 90°. Concen- 

 trated ammonia and sulphuric acid do not act at all on each other 

 below — 80° ; while above this temperature, a limited action takes 

 place by means of electric sparks, complete reaction suddenly 

 occurring at from — 80° to —65°. Sulphuric acid does not react on 

 common salt below —50° ; though at about this temperature a lim- 

 ited reaction begins which becomes complete at —25°. No action 

 takes place between sulphuric acid of 35 per cent and sodium or 

 calcium carbonates at —80°. Gas bubbles make their appearance 

 first at —56° with sodium carbonate and at —52° with calcium 

 carbonate; the reaction becoming turbulent at — 15° with the lat- 

 ter and at — 30° with the former carbonate. With nitric acids 

 chemical action begins at a slightly lower temperature. Me- 

 tallic sodium undergoes no change when brought into contact 

 with aqueous alcohol at — 78° containing 84 per cent alcohol; 

 the action beginning only at —48° and then being active. 

 Sodium may be mixed with 35 per cent H 2 S0 4 at —85° without 

 any action; but at — 50° a violent reaction occurs, the hydrogen 

 taking fire. With potassium, the action begins at —68°. At 

 — 85°, sulphuric acid may be mixed with an alcoholic solution of 

 barium chloride without precipitation, the reaction first occurring 

 at —70° and becoming complete at —40°. An alcohol solution of 

 silver nitrate was mixed at — 125° without reaction ; precipitation 

 beginning at —90° and being complete at —80°. Potassium 

 hydroxide dissolved in alcohol was mixed with phenol-phthaleim 

 at — 135° without action; a faint red tinge appearing at —100° 

 and the color being distinct at — 80°. Litmus in contact with 

 acids remains blue at — 120°, a sudden change to red taking place 

 with sulphuric acid at — 105° and with hydrochloric acid at —110°. 

 Hence the author concludes that no chemical action whatever 

 takes place at temperatures between — 125° and —155°. — C\ R. 

 cxv, 708, 814 ; J. Clxem. tioc, Ixiv, ii, 1 12, March, 1 893. g. f. b. 



6. Berzelius und Liebig, Hire Briefe von 1831-1845. 279 

 pp., 8vo. Munich and Leipsic, 1893. (J. F. Lbhmann). — The cor- 

 respondence of these illustrious chemists has been well edited by 

 Justus Carriere ; it is published under the auspices of the Royal 

 Bavarian Academy of Sciences. The book gives fascinating 

 glimpses of the personality of both these famous men — the fire 

 and enthusiasm of the younger Liebig and the calmer sagacity of 

 the Northern philosopher. The letters contain much that is of 

 historical interest to the student of chemistry, in giving many 

 descriptions ot the experiments and discoveries of both these cele- 

 brated investigators, many discussions of views and theories, and 

 numerous criticisms of the work of other chemists of the time. 

 The chief charm of the book, however, lies in the fact that the 

 letters are given literally and in full, even where written in ex- 

 citement and bitter animosity. These letters are supplemented 

 by extracts from others between Liebig and Wohler, so introduced 

 as to give a most effective form of explanation. h. l. w. 



