1869.] Physics. 469 



some experiments have been made by Kremers, who observed that, 

 in order to assist in expelling air from water, the addition of spirits 

 of wine, in the proportion of one part of the latter to three of the 

 former, is very useful. He cautions against a danger which exists 

 when such a mixture is heated too rapidly ; since it is very apt to 

 boil over, especially after a portion of the spirit has evaporated. It 

 is rather curious that, though both the water and spirits of wine 

 employed were pure, the mixture when boiling should assume a 

 greenish-yellow hue, which disaj)pears again on cooling. The 

 boiling-point of the fluid easily becomes as high as 109°. As a 

 result of a large number of experiments, the author finds that 

 water, as fully deprived of air as possible, may be heated as high 

 as from 180*^ to 200" C, without boiling permanently. 



M. Debray has investigated the action of heat upon the peroxide 

 salts of iron. In a large portion of distilled water a few drops of a 

 neutral solution of chloride of iron are poured, care being taken 

 not to apply so much of the salt that its colour is imparted 

 to the water ; on heating the hquid gradually up to, and above, 

 70° 0., it becomes perceptibly brown-coloured. When this moment 

 has arrived, the water no longer contains chloride of iron, but 

 instead a mixture of free hydrochloric acid and free peroxide of 

 iron ; the limpidity of the fluid is not, however, at all impaired. 

 In order to prove this, it is only requisite to pour into the fluid 

 a solution of common salt, whereby the static equilibrium of the 

 liquid is disturbed, and the oxide of iron precipitated. When the 

 experiment is made in sealed tubes, and the latter heated to between 

 200° and 300° C, crystalline oxide of iron is precipitated. 



A new freezing mixture, which appears to be of considerable 

 interest, has been described by Mr. Galletly. When citric acid 

 and crystallized carbonate of soda, in powder, are stirred toge- 

 ther, the mass gets into a pasty state, and m a short time becomes 

 quite liquid. If equivalent proportions of the substances are 

 used, the temperature falls from 60° F. to — 8°F. The mixture 

 for a time is full of air-bubbles, but soon becomes a clear, dense, 

 syrupy fluid. The fluid obtained by mixing the powders becomes 

 solid in a day or two standing in a corked jar. The solid mass has 

 the appearance of set j)laster of Paris or damp chalk. The addition 

 of a very little water appears to prevent this setting into a solid 

 mass ; but the chalky-looking citrate lies a long time in cold water 

 without being dissolved. 



Dr. H. Fleck, of Dresden, has instituted a series of experi- 

 ments with a view to obtain a non-poisonous paste for application 

 to lucifer-matches. He ascertained by some prehminary experi- 

 ments that sodium, when minutely divided along with explosive 



