137 
classed among acids. When an alcoholic solution of anthra- 
flavic acid is mixed with an alcoholic solution of potash, it 
assumes a dark yellow colour, and deposits on standing long 
orange-coloured needles arranged in stars and possessed of 
considerable lustre. The sodium compound prepared in the 
same manner crystallises in needles and resembles the 
potassium salt, but is lighter in colour. The ammonium salt 
may be obtained by dissolving the acid in boiling absolute 
alcohol and adding a slight excess of ammonia ; on cooling, 
the solution deposits dark yellow lustrous crystals. These 
crystals however, after a short exposure to the air, lose the 
whole of their ammonia, leaving a yellow residue consisting 
of the acid itself. This inability to retain ammonia even at 
the ordinary temperature of the atmosphere is a proof of 
the feeble nature of the acid. The potassium and sodium 
salts are also rather unstable compounds, for if it be attempted 
to recrystallise either of them from boiling water a portion 
of the acid separates, the solubility of the base in water 
being sufficient to overcome its affinity for the acid. Anthra- 
flavate of barium may be obtained by dissolving the acid in 
boiling baiyta water, or by adding chloride of barium to a 
solution of the substance in caustic alkali. It is deposited 
from its watery solution in small shining plates, and after 
being filtered off and dried has a fine maroon colour. Under 
the microscope it is seen to consist of small crystals with 
very regular outlines. It may be recrystallised from water 
without decomposition. The strontium salt is very similar, 
being soluble in boiling water and crystallising in long 
needles. The calcium salt is, however, insoluble in water, 
and is precipitated in orange-coloured flocks on the addition 
of chloride of calcium to an ammoniacal solution of the acid. 
On adding sulphate of magnesium to a solution of the acid 
in ammonia no precipitate is produced, but on standing 
some time the magnesium salt is deposited in dark yellow 
crystalline plates and needles arranged in star-shaped clus- 
