[681] But it is reprecipitated unaltered by excess of alkaline oxalate.

§ 691. Use in the Arts.—Oxalic acid is chiefly used by dyers and calico-printers, but also by curriers and harness-makers for cleaning leather, by marble masons for removing iron stains, by workers in straw for bleaching, and it is applied to various household purposes,[682] such as the whitening of boards, the removing of iron-mould from linen, &c. The hydropotassic oxalate (binoxalate of potash), under the popular names of “essential salt of lemons” and salts of sorrel, is used for scouring metals and for removing ink-stains from linen.

[682] A “Liquid Blue,” used for laundry purposes, contains much free oxalic acid.

§ 692. Hydropotassic Oxalate, Binoxalate of Potash, KHC2O4(H2O), is a white salt, acid in reaction, soluble in water, and insoluble in alcohol. Heated on platinum foil it leaves potassic carbonate, which may be recognised by the usual tests. Its aqueous solution gives, with a solution of acetate or sulphate of lime, a precipitate of calcic oxalate insoluble in acetic acid.

§ 693. Statistics.—Poisoning by oxalic acid is more frequent in England than in any other European country. In the ten years 1883-92, there were registered in England and Wales 222 deaths from oxalic acid—of these 199, or 89·6 per cent., were suicidal, the remainder accidental. The age and sex distribution of these cases is set out in the following table:—

POISONING BY OXALIC ACID IN ENGLAND AND WALES DURING THE TEN YEARS 1883-1892.

Accident or Negligence.
Ages,0-11-55-1515-2525-6565 and
above		Total
Males,1......2...1417
Females,.........15...6
Total,1......351423
Suicide.
Ages, 15-2525-6565 and
above		Total
Males, 91023114
Females, 2162285
Total, 301645199