Chemical Science. 339 



ing water, closed by a glass stopper, and inverted over mercury. 

 The alkaline solution was then introduced ; it should be previously 

 boiled, and if of potash or soda, freed from carbonic acid by baryta 

 water, ultimately the oxygen gas is introduced, and the whole 

 agitated from time to time. The same alkaline mixture, with the 

 exception of the oxygen, is preserved in a neighbouring tube, as 

 a standard, by which to appreciate the action of the oxygen gas. 

 The following are some of the results. 



Hematine. The solution of hematine or extract of log-wood 

 of a yellow orange colour, becomes blue by union with potash, 

 which may be preserved for six months without alteration, even 

 in sun-light ; but if it be in contact with oxygen, its blue colour 

 instantly changes, and gives place to a reddish yellow. No he- 

 matine remains. 0.2 grammes of hematine in 3 volumes of solution 

 of potash, when in contact with 20 volumes of oxygen, absorbed 

 in 10', 14 volumes of the gas; in 25', 24 volumes ; in one hour 15', 

 25.5 volumes ; and in 2 hours, 25. G volumes. Muriatic acid dis- 

 engaged 3 volumes of carbonic acid, and probably 3 volumes more 

 were retained by the liquor. 



The alkaline combination of hematine attracts oxygen with 

 such force, that 0.1 gramme of extract of log- wood dissolved in 

 2 cubic centimetres of potash water, reduced 25 cubic centimetres 

 of atmospheric air to pure azote, in 12 minutes. It may therefore 

 be used eudiometrically. 



The colouring principle of Brazil wood with potash water, forms 

 a purple combination, unalterable in years out of the contact of 

 oxygen; but that gas admitted, is absorbed, the solution becomes 

 of a reddish brown colour, and the substance is decomposed ; 0.1 

 gramme of extract of Brazil wood dissolved in 2 cubic centimetres 

 of potash water, absorbed 7.5 cubic centimetres in a quarter of an 

 hour, and 8.5 in 17 hours. Muriatic acid disengaged carbonic 

 acid ; the whole quantity being perhaps 3.5 cubic centimetres. 



Cochineal forms with potash water a fine purple solution, 

 sensibly unaltered in a twelvemonth. Contact of oxygen makes 

 it pass to yellow, and the colouring principle is destroyed. 



Colour of violets also appeared to act in a similar manner ; but 

 it was impossible to free the solution from air, and, consequently 

 oxygen, inasmucli as it would not sustain ebullition. 



Flax put into contact with potash water gave colour to.it, which, 

 in contact with oxygen, caused absorption of the latter. The 

 ligneous part of the flax did not produce this effect. 



Gallic acid. M. Chevreul shewed, in 1S14, that permanent 

 gallates of potassa, soda, baryta, strontia, and lime, could not be 

 obtained, operating in contact with the air, because the oxygen 

 re-acted, rendered the solutions blue, green, and purple, and de- 

 stroyed the acid. Gallic acid forms soluble colourless salts with 

 potash and soda. Insoluble white and crytalline salts with baryta, 



