





AOD Pie. ae LE DT i ete sles 
35. Reduction of Fehling’s Solution to Metallic Copper— 
a Method of Depositing a Shining, Mirror-like 
Film of Copper on Glass Vessels. 
By PaXcuAnan Neoai, M.A., Professor of Ohemistry, Rajshahi 
College. 
iebig first demonstrated that silver may be deposited on 
glass vessels by reducing an ammoniacal solution of silver oxide 
by means of chemical reagents (Liebig, Annalen, 1835, xiv, 133). 
The method has received an industrial application in the prepa- 
ration of mirrors; and various substances such as tartarates, 
rous condition, is difficult to obta n by reduction from cupric 
compounds by means of organic ccagenke, as the reduction should 
pass eck an intermediate stage of cuprous compounds before 
metallic copper may be deposited. In the case of silver, 
oe aa reduction of bag salts metallic silver is direct. 
Faraday (Phil. Trans. 1857, p. 145) obtained a deposit of 
snotellio « eh by dissolving copper poeta in olive oil, and heat- 
pbemtond of a glass by means of a Leyden battery in an 
a, of hydrogen. Wright (Silliman’s Amer. Journ., 1877, 
ph es discharge between copper electrodes. The firm of Weiso- 
kupf obtained it by a complicated anion! process, Chattaway 
in a paper read before the Royal Society of London on m 
21, 1907, has obtained shining deposits of copper by first redu- 
cal solution of copp y e 
mereng Mes phenylhydrazine, and then heating the solution 
cent. caustic potash solution. In the present investi- 
gation it “ath been shown that brilliant depoars of copper may be 
obtained on glass vessels by reducing Fehling’s Solution, under 
special circumstances, by means of formaldehyde. 
ay od s Solution (Annalen 72, 106; 106, 75) as is well 
kno vig reduced by aldehydes and other organic reducing 
nts ae tee cuprous oxide, but the reduction of the solution by 
means of formaldehyde to metallic copper which deposits on glass 
vessels as a shining layer is, to my arta, new. The follow- 
ing details, if followed, give good results. The usual solutions of 
ch sulphate and alkaline tartarate are prepared and kept in 
bo 
