Miscellanies. 399 
Three other substances, saccharic acid, salicylic acid and pyromeconic 
acid, were also known to possess the same property, though the coatings 
which they yield are much darker, and therefore less beautiful than those 
formed by aldehyde. This was the state of our knowledge previous to 
the announcement, about six months ago, of Mr. Drayton’s process for 
silvering mirrors in the cold, by means of ammonio-nitrate of silver and 
an alcoholic solution of the oils of cloves and cassia. 
I find that the number of substances which, especially when assisted 
by heat, give more or less brilliant coatings of reduced silver, is much 
greater than has hitherto been supposed. Thus grape sugar forms a 
pretty brilliant mirror even in the cold. When unassisted by heat the 
mirror is rather slowly formed, requiring from six to twelve hours; but 
when a slight heat is applied it forms very readily in the course of a few 
minutes ; the coating is much darker than that produced either by alde- 
hyde or by Drayton’s process. Cane sugar also yields a mirror when as- 
sisted by heat, but none in the cold. Gum-arabic and starch also yield 
dark colored mirrors, but more slowly, and require considerable boiling : 
so do phloridzine and salicine. Oils of turpentine and laurel also give 
mirrors, but with still greater difficulty, the solutions requiring to be very 
concentrated. Resin of guaiacum acts in a similar manner. 
Oil of pimento, as is well known, consists of two oils, one an acid oil, 
which is heavier than water, and forms crystalline compounds with the 
bases; this in the course of a few minutes, even in the cold, produces as 
brilliant a coating of silver as the mixture of the oils of cassia and cloves. 
The neutral portion of the pimento oil, which is lighter than water, does 
not reduce nitrate of silver even after long boiling. I could not succeed 
in forming metallic mirrors with cinnamic, benzoic, meconic, komenic, 
tannic, or pyrogallic acids, with gum benzoin, elemi or olibanum, with 
oil of rhodium or with glycerine. 
Ingenious as Mr. Drayton’s patent process certainly is, it labors under a 
very serious inconvenience, which I greatly fear will not be easily remedied. 
In the course of a few weeks the surfaces of the mirrors formed by his 
process become dotted over with small brownish-red spots, which greatly 
injure their appearance. The cause of the spots seems to be this—that 
the metallic silver while beinz deposited on the surface of the glass car- 
ries down with it mechanically small quantities of a resinous matter, re- 
sulting, most probably, from the oxidation of the oil. ‘This resinous mat- 
ter, which is interposed between the glass and the silver, in the course of 
time begins to act on the metallic surface with which it is in contact, and 
to produce the small brown spots already mentioned. If an excess of the 
essential oils is employed to precipitate the silver, the metallic mirror is 
much darker, and gets sooner discolored than usual. No doubt the alco- 
hol present in the solution keeps up much of the resinous matter ; still a 
little of it is almost always deposited on the silvered surface, and acts in 
the injurious way described.— Proceedings of Chem. Soc., Part 10. 
