Gilding Glass. In looking over some volumes of the Journal fuer praktische Chemie, I came across a method of gilding glass due to Boettger (Journ. f. prakt. Chem. 103, p. 414). After many trials I believe I am in a position to give definite instructions as to the best way of carrying out this rather troublesome operation. The films of gold obtained by the process are very thick, and the appearance of the gold exceedingly fine. The difficulty lies in the exact apportionment of the reducing solution. If too much of the reducing solution be added, the gold deposits in a fine mud, and no coating is obtained. If, on the other hand, too little of the reducing solution be added, little or no gold is deposited. The secret of success turns on exactly hitting the proper proportions. The reducing solution consists of a mixture of aldehyde and glucose, and the difficulty I have had in following Boettger's instructions arose from his specifying "commercial aldehyde" of a certain specific gravity which it was impossible to reproduce. I did not wish to specify pure aldehyde, which is not very easily got or stored, and consequently I have had to determine a criterion as to when the proportion of reducing solution is properly adjusted. The aldehyde is best made as required. I employed the ordinary process as described in Thorpe's Dictionary of Applied Chemistry, by distilling alcohol, water, sulphuric acid, and manganese dioxide together. The crude product is mixed with a large quantity of calcium chloride (dry--not fused), and is rectified once. The process is stopped when the specific gravity of the product reaches 0.832 at 60 deg. F. The specific gravity of pure aldehyde is 0.79 nearly. The following is a modification of Boettger's formula:- Solution I 1 gram of pure gold is converted into chloride--got acid free--i.e. to the state represented by AuCl3, and dissolved in 120 cc. of water. This solution is the equivalent of one containing 6.5 grains of trichloride to the ounce of water. Solution II. 6 grams sodium hydrate. 100 grams water. Solution III. 0.2 grams glucose (bought as pure). 12.6 cubic centimetres 95 per cent alcohol. 12.6 cubic centimetres water. 2.0 cubic centimetres aldehyde, sp. gr. 0.832. To gild glass these solutions are used in the following proportions by volume:- 16 parts of No. I. 4 parts of No. II. 0.8 parts of No. III. The glass is first cleaned well with acid and washed with water: it is then rinsed with Solution No. III. If it is desired to gild the inside of a glass vessel, Solution No. III. may be placed in the vessel first, and the walls of the vessel rinsed round carefully. Solutions I. and II. are mixed separately and then added to III.--after about two minutes the whole is well shaken up.