may be used. I constructed some angular tubes of long narrow slips of glass and wood, placing three or four together, so as to form a triangular or square tube, tying them round with pack thread, and easily obtained tones from hydrogen by means of them; and it is evident that variations of the channel, the use of which is to form and direct the current of air, may be made without end.—May 11, 1818.
Boracic Acid, action on Turmeric[1].
It may be observed, in connexion with the changes of colour produced by acids, that boracic acid reddens turmeric paper in all states of dilution. When a very weak solution is used, it requires a few minutes to produce the effect; but when produced, it exactly resembles that of alkali. It has been said that strong solutions of alkaline borates, which have been made purposely acid, have become alkaline on being diluted. This has probably arisen from a careless observance of the effect above noticed, and a want of corroboration by the effect on litmus paper of the diluted solution. I find that solutions once made acid redden litmus paper, however diluted; though at the same time they also redden turmeric paper. Paper coloured by rhubarb is not affected in this way.
Boracic Acid[2]
I mentioned above the property possessed by boracic acid in all states of dilution, of reddening turmeric paper in the manner of an alkali. Since then the attention of M. Desfosses has been drawn to the action of boracic acid on this colouring matter (Annales de Chimie, xvi. p. 75), apparently without a knowledge of the previous remark; and he has shown that a mixture of boracic with other acids, reddens turmeric very deeply, and that turmeric, when acted on by this mixture of acids, has its nature altered, for it approaches somewhat to turnsole, and is rendered blue by alkalies.
There is something so curious in this action of boracic acid on turmeric, that I am tempted to offer a few more results on the subject.
