Chemical Science. 633 



0.100 of camphor yielded at 23 and 27" 9"' Barom. 162 cc. of gas. 

 0.100 21 27 9 164 



and 0.255 of camphor gave 0.230 of water, 



0.225 0.191 



of which tlie mean result would be, 



Carbon 81.763 or 12 atoms. 



Hydrogen .... 9.722 18 

 Oxygen .... 8.535 1 

 or 6 ( 2C + 3 H) + O. 



Camphoric acid, being expressed by 10 C + 15 H + 5 O, con- 

 sists accordingly of camphor with 5 atoms of oxygen for eyery atom, 

 but so that 5 atoms of camphor would form 6 atoms of camphoric 



i it * 



acid*. 



23. USE OF MICA IN MINUTE CHEMICAL ANALYSES. 



Mica is not broken or burnt by flame ; M. Voges, therefore, sepa- 

 rates a thin film with a knife, and if he has to heat a substance, puts 

 it upon the mica and a lamp beneath. If many successive experi- 

 ments are to be made, a wet cloth removes the remains of former 

 experiments. Slight detonations, concentrations, evaporations, com- 

 bustions, reductions of metals, &c., may thus be made with great 

 facility. The thinness of the mica allows the heat to pass with 

 great readiness ; its transparency allows changes of colour to be 

 seen. The blowpipe cannot often be used because it renders the 

 mica white. On concentrating some drops of acetic, nitric, sulphuric, 

 muriatic, phosphoric, and tartaric acids upon mica by the flame of a 

 candle, phosphoric acid was the only one which left a visible mark. 

 Caustic potassa might be fused on it without sensible action. Nitrate 

 of silver, reduced upon it by heat, allowed the metal to be wiped 

 off, leaving no mark. Nitrate and acetate of lead could be decom- 

 posed upon it without change. Tartrate of potash and antimony, 

 calomel, sulphur, &c. could be heated powerfully on it without altera- 

 tion to the plate. Mica, therefore, may be used as a very valuable 

 agent in the laboratory t- 



24. ON PERFORATING AND CUTTING GLASS, EARTHENWARE, &c. 

 (Mr. Marsh.) 



Although many persons are acquainted with methods of perforating 

 glass, &c. the following easy one I find is not so generally known 

 as it deserves to be, and I am therefore induced to explain the mode of 

 operating I employ, in order to produce the best results. Circum- 

 stances often conspire to render the process valuable to persons 

 situated at a distance from large manufacturing towns, and especially 

 to those who are living in places where they cannot readily obtain 



* Extracted from Poggendorf's Annal., Bd. xx. St. 1. p. 41. sq. 

 f Journal de Pbarmacie, 1831, p. 113. 



