208 Miscellaneous Intelligence, 



M. Savart then stated, and proved by the evidence of M. Duldng, 

 Chevreul, and others, that his results were obtained in August and 

 September, 1827. 



13. Method of collecting Air for Analysis, — Chemists frequently 

 have occasion to collect air from particular situations, for the pur- 

 pose of analyzing it. When the air contains no substance soluble 

 in water, a iDottle filled with water being opened in the place, and 

 the liquid poured out, becomes filled with the air, and may then be 

 closed. If there be gases or vapours present, which act on, or are 

 dissolved in water, as sulphuretted hydrogen or carbonic acid, then 

 mercury is usually employed in place of water. M. Gaultier de 

 Claubry thought that some saline solution might be found, which 

 having Httle or no solvent power over these substances, might be used 

 for the purpose, and ultimately found such a one in a saturated 

 solution of sulphate of magnesia, made by dissolving in 1 part of 

 water, 1 part of the crystallized salt, or half a part of the anhydrous 

 salt, using a slight elevation of temperature for the purpose, and 

 then allowing the liquid to cool. Experiments were made on the 

 solvent power of this solution, and also of water and saturated so- 

 lutions of sulphate of soda and nitrate of potash ; the two latter were 

 scarcely better than water, for being mixed with their bulk of car- 

 bonic acid, they dissolved nearly eight-tenths of it, whilst the sul- 

 phate of magnesia solution dissolved only two-tenths ; and when tried 

 with sulphuretted hydrogen, they dissolved above nine-tenths^ and 

 the sulphate little more than five-tenths. 



Mixtures of air with a few hundreths of these two gases when 

 agitated with the solution of sulphate of magnesia, lost very little 

 of the gases, and only with difficulty. A bottle filled with the solu- 

 tion, and then opened in such mixtures of air, was filled with the 

 mixture without any sensible change being produced on it by the 

 solution. In experiments made at certain sewers at Paris, where 

 air had to be obtained from depths and situations to which men 

 could not pass, the use of the solution was found to give the same 

 results as the use of mercury. 



Sulphate of magnesia is a cheap salt, and may, therefore, be very 

 useful in these and similar circumstances. — Ann. de Chimie. xxxvii. 

 380. 



14. On the Hypo-phosphites. — M. Rose has been engaged in a 

 general investigation of these salts, and his memoir is inserted in 

 the Annal. der Physik und Chemic, 1828, p. 77. The hypo-phos- 

 phites of lime, baryta, and strontian, may be prepared by boiling 

 the earths with phosphorus and water. In preparing that of lime, 

 the phosphorus should not be added before the milk of lime boils, 

 and the operation should be continued until all the phospliorus has 

 disappeared, and the pecuhar smell has ceased. Carbonic acid is 

 then to be passed through to separate the excess of caustic lime, the 



