Chemical Science. 197 



3 or 4 cubic inches, and filled with dry air, and inserting into the 

 vessel a few grains of the suboxide of platina, on a small plate sus- 

 pended by a platina wire, at the end of a few minutes it is observed 

 that the whole interior surface of the vessel becomes moist, and 

 that this moisture collects into small drops, which make litmus 

 paper red. This experiment succeeds well, particularly under the 

 influence of light, and the suboxide becomes hot, although the 

 acetic acid evaporates at the very moment of its formation. To 

 determine the quantity of alcohol contained in a liquid, as in wine, 

 beer, &c, a particular apparatus is to be employed, which commu- 

 nicates with a graduated glass jar filled with oxygen gas. In this 

 apparatus, small quantities of the liquid containing alcohol are ren- 

 dered acid in a few hours ; and from the volume of oxygen con- 

 sumed, the quantity of alcohol contained in the liquid subjected to 

 experiment is calculated, (100 parts of absolute alcohol combine 

 with 69.5 parts of oxygen to pass into the state of acetic acid.) 

 M. Dobereiner promises ample details respecting his apparatus, to 

 which he gives the name of Acetogenator. — Jahrb. der Chemie. und 

 Physik, No. 12. 



■ 

 41. Crystallization of Sulphated Iron, by A. H. Van der Boon 

 Mesch, of Leyden. — These crystals, which are found in the mine of 

 Gieshiibel de Silberberg, in Bavaria, surpass in size, transparency, 

 and regularity, all that it is possible to obtain by art, although M. 

 Brongniart says, that they are rarely, if at all, found in nature ; 

 they are grouped round quartz flints of different sizes. Some 

 crystals have the forms of oblique rhomboidal prisms, others of the 

 Fer sulfate base', of Hauy. In general, the edges are not very 

 angular, and the faces regular and united ; their specific gravity 

 is 2.037. They are of a clear green colour, soluble in cold water, 

 and their solution is blackened by gallic acid. When they are ex- 

 posed to the open air, the crystals alter ; they become brown, and 

 decompose into a powder of different colours, so that this mineral 

 must be preserved with care. The first change it undergoes is to 

 pass into the state of sulphate of iron, which perhaps has given rise 

 to the opinion that this salt did not exist in nature. When this 

 salt is heated in a retort, sulphurous acid is disengaged, which 

 may be detected by Brazil wood paper ; and when it is exposed 

 to a white flame, it becomes black and magnetic. It is soluble 

 in phosphate of ammonia, which tranforms it into a glass some- 

 times red, sometimes yellow, which passes, after cooling, into a dull 

 green. Melted again in this state with salt of phosphorus, it be- 

 comes of a very pure green. The same phenomena takes place 

 with borax. The analysis which Berzelius, Bergmann, and Mit- 

 scherlich have made of this substance, gives 23.27 parts of oxide 

 of iron, 28.39 parts of sulphuric acid, 38.45 parts of water. 

 The formation of this mineral is attributed to the natural decom- 

 position of sulphuret of iron in calcareous stone. — liydrag. tot. de 

 Nat. Wet. N. iv. p. 2. 



