MECHANICS AND USEFUL ARTS. 107 



electro-plating. The proportion of glycerine and litharge to be 

 taken must depend somewhat upon the consistency of the cement, 

 and its proposed uses. An excess of glycerine would retard the 

 setting, as it does not readily evaporate. This new use of glycer- 

 ine adds another application to a substance that only a few years 

 ago was thrown away. 



CHINESE GOLD-LACKER. 



The gold-lacker lining of a Chinese cabinet in the Museum at 

 Cassel peeled off, and thus gave Dr. Wiederhold the opportunity 

 of studying the composition of this substance. On examining it 

 lie found particles of tin foil attached to the lacker; so he comes 

 to the conclusion that this material formed the ground upon 

 which the lacker varnish was laid. His attempts to imitate the 

 varnish were perfectly successful, and he gives the following 

 directions for the preparation of a composition which closely 

 resembles the true Chinese article. First of all, 2 parts of copal 

 and 1 of shellac are to be melted together to form a perfectly 

 fluid mixture, then 2 parts of good boiled oil, made hot, are to be 

 added ; the vessel is then to be removed from the fire, and 10 

 parts of oil of turpentine are to be gradually added. To give 

 color, the addition is made of solution in turpentine of gum gutta 

 for yellow, and dragon's blood for red. These are to be mixed 

 in sufficient quantity to give the shade desired. 



MALLEABLE PROPERTIES OF CHINESE BRONZE. 



The "Journal of Applied Chemistry" thinks the unsuccessful 

 attempts made to manufacture Chinese gongs and bells, in Europe 

 and tlie United States, are due to the mistake that was made of 

 hammering the Chinese alloy at the ordinary temperature, instead 

 of working it at a high temperature, according to the recent dis- 

 covery made by Professor Riche, of Sorbonne, Avho has been per- 

 fectly successful in his experiments made on a large scale at the 

 Paris Mint. 



The different analyses have shown that the Chinese alloy was 

 formed of a certain proportion of tin and copper, in the propor- 

 tion of 20 parts of tin to 80 of copper. Ingots of bronze were cast 

 containing 21.5, 20.0, 18.5 per 100 of tin; these were afterward 

 submitted to the action of the hammer, at temperatures varying 

 from the ordinary temperature to a red heat. At the ordinary 

 temperature the metal was as brittle as glass, but approaching 

 300 to 350 Centigrade a sensible amelioration was noticed. At 

 a dark-red heat it appears that the condition of the metal is quite 

 different, as this alloy can be worked as easily as iron or bronze of 

 aluminium. 



The metal flattened without cracking under the most powerful 

 blows of enormous hammers, and can be reduced without the 

 slightest difficulty to sheets of one millimetre thickness. These 

 sheets have exactly the appearance of the Chinese bronze, and pos- 

 sess great flexibility. 



