The solution reddens litmus and is an astringent.
In the second group, we may notice the application of litmus, methyl orange or phenolphthalein in alkalimetry, when the acid or alkaline character of the solution commands the colour which it exhibits; starch paste, which forms a blue compound with free iodine in iodometry; potassium chromate, which forms red silver chromate after all the hydrochloric acid is precipitated in solutions of chlorides; and in the estimation of ferric compounds by potassium bichromate, the indicator, potassium ferricyanide, is placed in drops on a porcelain plate, and the end of the reaction is shown by the absence of a blue coloration when a drop of the test solution is brought into contact with it.
They are soluble in water, have an astringent, acid, and sweetish,, .taste, react acid to litmus, and crystallize in regular octahedra.
An alkali is distinguished from an acid or neutral substance by its action on litmus, turmeric and other indicators.
In the solution, therefore, there is now an excess of hydroxyl ions; consequently it has an alkaline reaction and the litmus turns blue.
The free acid turns blue litmus to a claret colour.
The solution of arsenious oxide in water reacts acid towards litmus and contains tribasic arsenious acid, although on evaporation of the solution the trioxide is obtained and not the free acid.
Gummic acid reddens litmus, its reaction being about equal to carbonic acid.
How had their conversation gone from an inquiry about money to a litmus test of their stay in Texas?
In other cases, such as that of litmus, both the ion and the undissociated molecule are coloured, but in different ways.
They are neutral to litmus and do not combine with dilute acids or bases; strong bases, such as lime and baryta, yield saccharates, whilst, under certain conditions, acids and acid anhydrides may yield esters.
Boric acid (q.v.) being only a weak acid, its salts readily undergo hydrolytic dissociation in aqueous solution, and this property can be readily shown with a concentrated aqueous solution of borax, for by adding litmus and then just sufficient acetic acid to turn the litmus red, the addition of a large volume of water to the solution changes the colour back to blue again.
For example, various sugars - lactose, glucose, saccharose, &c. - are added to test the fermentative action of the bacterium on these substances; litmus is added to show changes in reaction, specially standardized media being used for estimating such changes; peptone solution is commonly employed for testing whether or not the bacterium forms indol; sterilized milk is used as a culture medium to determine whether or not it is curdled by the growth.
At about the same time Boyle investigated several acids; he established their general reddening of litmus, their solvent power of metals and basic substances, and the production of neutral bodies, or salts, with alkalies.
The aqueous solution is strongly acid to litmus and dissolves most metals directly.
By adding certain alkalies to the other ingredients used in the preparation of these pigments, the colour becomes indigoblue, in which case it is the litmus of the Dutch manufacturers.
It is a white crystalline solid, easily soluble in water, the solution showing a strongly acid reaction with litmus; the colour, however, is ultimately discharged by the bleaching power of the compound.