By A. Robertson and J. Hofmann.
The authors draw lines across the letters or figures with quill pens dipped in the following reagents, and observe the changes where the ink and the reagent meet, using, if needful, a magnifying power of 100 diameters. The reagents are: (1) a 3 per cent. solution of oxalic acid; (2) a 10 per cent. solution of tartaric acid; (3) a 2 per cent. solution of chloride of lime; (4) a solution of 1 part stannous chloride in 1 part hydrochloric acid and 10 parts of water; (5) sulphuric acid at 15 per cent.; (6) hydrochloric acid at 10 per cent.; (7) nitric acid at 20 per cent.; (8) saturated solution of sulphur di-oxide; (9) 4 per cent. solution of gold. chloride; (10) solution of 1 part potassium ferro-cyanide in 1 part hydrochloric acid and 10 parts water; (11) solution of one part sodium thiosulphate (hyposulphite ) in 1 part ammonia and 10 parts water; (12) 4 per cent. soda lye.
The subjoined table shows the results. The results with tartaric acid are not tabulated.
— Chemiker Zeitung.
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