The Deposition of Silver Films on Glass

Alexander. Silverman, Raymond M. Howe
1917 Journal of Industrial & Engineering Chemistry  
The purpose of t h e investigation was threefold: t o produce t h e best mirrors possible, with t h e highest possible percentage deposition, and a t room temperature, if possible. The work naturally divides itself into two parts. I n t h e first part mirrors were studied from a qualitative standpoint. I n t h e second part the most satisfactory processes were studied quantitatively. PART I-QUALITATIVE At first the qualitative results obtained in a previous investigation2 were duplicated and t
more » ... e duplicated and t h e most promising methods studied more thoroughly. Methods involving t h e use of sugars, tartrates and formaldehyde as reducing agents were included. Accordingly, molar solutions were made of potassium tartrate, tartaric acid, milk sugar and cane sugar. A 0 . 2 molar solution of silver was made b y nearly dissolving the ammonia precipitate in AgN03 solution, b y t h e addition of more ammonium hydroxide, and diluting with water t o the rCquired volume. The formaldehyde used was a 40 per cent solution. The volumes given in the tables were used and in each case enough water was added t o make a total volume of 2 0 cc. This made a convenient total for test-tube mirrors. SERIES I (Nos. 1-12) involved t h e use of potassium tartrate as a reducing agent. I t shows very clearly Assumptions regarding the influence of concentration were verified. The silver nitrate concentration which gave the best results, was a t least 0 . I 5 molar. When the concentration of t h e tartaric acid was as high as 0 . 2 molar no mirrors resulted. When of 0.1 molar concentration no mirrors resulted with silver solutions which were of less t h a n 0.15 molar concentration. The stronger solutions of tartaric acid gave white precipitates which sometimes redissolved. With tartaric acid solution of 0 . 0 2 5 molar concentration and t h e silver nitrate 0.15 t o 0.2 molar concentration t h e best mirrors resulted. More silver nitrate t h a n this was unnecessary-less tartaric acid was insufficient for a satisfactory reaction. I n general, the silver nitrate concentrations which gave the best results were greater t h a n 0.15 molar. The concentration of t h e reducing agent had t o be less than 0.1 molar under t h e conditions of experiment. SERIES I11 (Nos. 25-36)-The series in which milk .sugar was used as t h e reducing agent was extremely gratifying. The solution when heated t o about 80'-85" C. turned black and then t h e mirror began t o form. This formation was uniform and gradual and did not tend t o deposit in spots as did many of t h e other mirrors. The mirrors formed whether the silver solution was 0.2 molar or only 0.01 j molar concentration. The 0 . 2 molar solution was stronger t h a n necessary but gave good results. The 0.015 molar solution was not strong enough t o produce a mirror of desirable thickness. All intermediate concentrations gave good RESULTS WITH~VARIOUS REDUCING AGENTS
doi:10.1021/ie50095a024 fatcat:ge3rpae4yjgdhlxcchcfxmyisi