In Germany the officinal acid is of 1·185 specific gravity, corresponding to about 30 per cent. of HNO₃. The dilute nitric acid of the Pharmacopœia is a colourless liquid, of specific gravity 1·101, and should contain about 17·4 per cent. of acid. The acids used in various industries are known respectively as _dyers’_ and _engravers’_ acid. _Dyers’_ acid has a specific gravity of 1·33 to 1·34 (66° to 68° Twad.), that is, strength from 56 to 58 per cent. of HNO₃. _Engravers’_ acid is stronger; being of 1·40 specific gravity (80° Twad.); and contains 70 per cent. of HNO₃. Although the _pure_ acid of commerce is (and should be) almost colourless, most commercial specimens are of hues from yellow up to deep red. An acid saturated with red oxides of nitrogen is often known as “fuming nitric acid.” § 80. =Use in the Arts.=--Nitric acid is employed very extensively in the arts and manufactures. The dyer uses it as a solvent for tin in the preparation of valuable mordants for calico and other fabrics; the engraver uses it for etching copper. It is an indispensable agent in the manufacture of gun-cotton, nitro-glycerin, picric acid, and sulphuric acid; it is also used in the manufacture of tallow, in preparing the felt for hats, and in the gilding trades. It is said to be utilised to make yellowish or fawn-coloured spots on cigar leaves, so as to give them the appearance of age and quality. It is also used as a medicine. § 81. =Statistics of Poisoning by Nitric Acid.=--In the ten years 1883-1892 no case of murder was ascribed to nitric acid, but it caused accidentally 25 deaths, and was used in 27 cases of suicide. The following tables give the age and sex distribution of these deaths:-- DEATHS IN ENGLAND AND WALES DURING THE TEN YEARS ENDING 1892 FROM NITRIC ACID. ACCIDENT OR NEGLIGENCE. Ages, 1-5 5-15 15-25 25-65 65 and Total above Males, 6 2 1 9 ... 18 Females, 3 ... ... 4 ... 7 -------------------------------------- Totals, 9 2 1 13 ... 25 -------------------------------------- SUICIDE. Ages, 15-25 25-65 65 and Total above Males, 3 14 1 18 Females, 1 8 ... 9 ---------------------------- Totals, 4 22 1 27 ---------------------------- § 82. =Fatal Dose.=--The dose which causes death has not been ascertained with any exactness. As in the case of sulphuric acid, we may go so far as to say that it is possible for a few drops of the strong acid to be fatal, for if brought into contact with the vocal apparatus, fatal spasm of the glottis might be excited. The smallest dose on record is 7·7 grms. (2 drachms), which killed a child aged 13.