211: ANNUAL OF SCIENTIFIC DISCOVERT. 



raents on this subject, the general result of which may be summed 

 up as follows : — 



(1.) The action of boiling liquids upon glass vessels is, Avithin 

 certain limits, proportional to the time of boiling. The action 

 upon ni'W vessels is somewhat greater for the lirst few hours than 

 altcnvards. 



(2.) Tiie action is proportional to the extent of surface in con- 

 tact with the boiling liciuid. 



(3.) Tiie action is independent of the quantity of liquid evapo- 

 rated in a given time. 



(4.) The action decreases rapidly with the temperature. 



(5.) Alkalies, even in very dilute solutions, attack the glass 

 strongly. 



(G.) Dilute acids (with the exception of sulphuric acid) attack 

 the glass less than pure water. 



(7.) Solutions of salts whose acids form insoluble calcium salts 

 attack the glass more violently, those whose acids form soluble 

 calcium salts less violently, than pun^ water. 



(8.) The amount of action depends on the composition of the 

 glass, soda glass being attacked more than Bohemian glass. 



(9.) The component parts of the glass are dissolved in about 

 the proportions in which the}'' exist in the glass. 



(10.) Vessels of Berlin porcelain were sensibly attacked by 

 alkalies only. 



DECREASE OF TEMPERATURE CAUSED BY THE SOLUTION OF 



SALTS IN WATER. 



The decrease of temperature caused by the solution of a given 

 salt in water is greater the larger the quantity of the salt dis- 

 solved in a given time. Since, however, the amount of the salt 

 which can be dissolved by water of a given temperature is a 

 fi.xed quantity, it follows that the maximum decrease of tempera- 

 ture will be produced by (uiiploying a quantity of salt sufficient 

 to form a saturated solution. As the decrease of temperature 

 will be greater the more rapid the solution, the salt employed 

 should be in as fine a state of division as possible ; moreover, the 

 relative decrease of temperature is greater, the lower the tem- 

 perature of the water, and of the salt before mixing; therefore, 

 the greatest effect will be obtained by cooling each separately 

 before making the solution. In no case is it possible to obtain a 

 temperature lower than the fieezing-pointj^of tli^ saturated solu- 

 tion, although that point can in some cases be very closely ap- 

 proached. A number of experiments made upon various salts, 

 were conducted in the following manner: — The finely powdered 

 salt and the requisite quantities of water were, previous to the 

 making of the experiments, each put in separate beakers made 

 of very thin glass, and placed for from 12 to 18 hours in a room 

 wherein the temperature could i)e kept as nearly as possible con- 

 stant; in consequence of this, the beakers and contents attained 

 the same temperature throughout. The mixirig was efTected by 



