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Progress in Science. 
sometimes blackened by sulphuretted hydrogen. M. Lenoir has happily suc- 
ceeded in overcoming these defe&s by a process alike simple and free from 
objections on sanitary grounds. The glass, silvered as above, is washed, and 
then sprinkled with a dilute solution of the double cyanide of mercury and 
potassium. The silver displaces a part of the mercury and enters into solution, 
whilst the rest of the silver forms an amalgam whiter and much more adhesive 
to glass than pure silver. The transformation is instantaneous. The amount 
of mercury fixed does not exceed 5 to 6 per cent. The glass thus prepared is 
free from the yellowish tint of pure silver : it is also less attacked by sulphur 
vapours and the rays of the sun, in which last respedl it is superior to mirrors 
silvered by the old process. 
An examination of French red wines for genuineness of colour has been 
made by M. Eugen Dietrich. The red of genuine wines appears brownish in 
thin layers ; if diluted with 50 parts of water its colour is very faint ; whilst 
artificially coloured wines appear decidedly blue-red, even at such a degree of 
dilution. If diluted with 20 parts by weight of water the behaviour of genuine 
wines as compared with spurious was as follows : — Acetate of Lead 1 : 10. — In 
genuine wines colour disappears ; liquid becomes dirty and turbid. On heating, 
small silver-grey flakes with a slight reddish tint appear. Spurious wines 
yield large curdy flakes of a deep violet-blue, which on heating becomes more 
decided. Sulphate of Copper 1 : 10. — In genuine wines the colour disappears 
almost entirely; without turbidity. Spurious wines turn violet-blue, with a 
slight turbidity. Baryta Water 1 : 10. — Genuine wines lose their colour almost 
entirely ; faint turbidity. Spurious wines turn violet-blue, or greenish blue and 
turbid. Filter-paper steeped in the above tests, and dried, becomes colour- 
less if moistened with genuine wine, whilst coloured sorts give a violet or 
blue spot. 
