CHEMICAL SCIENCE. 163 



The melting point is 85, the boiling 1 point 113. With water much 

 heat is evolved, and solution takes place without the escape of gas; 

 the solution forms nitrates. Decomposition takes place so near the 

 boiling point of the crystals, that the density of the vapor cannot 

 well be determined. On attempting to recrystallize the substance in a 

 sealed tube, in which it had been suffered to liquefy, a violent ex- 

 plosion took place. 



LIQUID PROTOXIDE OF NITROGEN. 



M. DUMAS has recently communicated to the Paris Academy of 

 Sciences an account of the method used by him in effecting the 

 liquefaction of large quantities of protoxide of nitrogen. He used a 

 force-pump constructed for the purpose, securely bound with a belt 

 of iron. He so arranged it that, the reservoir being surrounded by 

 ice, the body of the pump was cooled by a circulation of water around 

 it, and even the stem of the piston was always moistened by cold 

 water. He then compressed into the reservoir in the course of two 

 hours 200 litres* of gas, of which 20 suffice to produce a pressure of 

 30 atmospheres, about which liquefaction commences. The remain- 

 der of the gas furnishes a liquid. Once compressed, the liquid gas 

 may be preserved in the reservoirs for a day or two, but if the stop- 

 cock is opened the gas escapes, and a portion freezes at first, but soon 

 flows in a liquid state ; the solid portion resembles a mass of snow. 

 It melts upon the hand, and rapidly evaporates, leaving a severe burn. 

 The liquid portion, which is far the most abundant, if received in a 

 glass keeps for half an hour, even in the open air. 



The protoxide of nitrogen is liquid, colorless, very mobile, and 

 perfectly transparent. Metal dropped into it produces a hissing 

 noise like that of red-hot iron plunged in water. Quicksilver causes 

 the same noise, freezes, and affords a hard brittle mass resembling 

 silver in color. Potassium floats upon the liquid and experiences no 

 change, and the same is the case with charcoal, sulphur, phosphorus, 

 and iodine. Ignited charcoal floats and burns with brilliancy. Sul- 

 phuric acid and concentrated nitric acid freeze. Water is converted 

 to ice with a slight explosion. SiMmaris Journal^ July. 



AN ANCIENT ART REDISCOVERED. 



AT a late meeting of the Asiatic Society of London, a human hand 

 and a piece of beef preserved by means of a preparation of vegeta- 

 ble tar, found on the borders of the Red Sea in the vicinity of Mocha, 

 were presented ; a specimen of the tar accompanied them. Col. 

 Hold, who presented the specimens, observes, " During my resi- 

 dence on the Red Sea, a conversation with some Bedouin Arabs, in the 

 vicinity of Mocha, led me to suspect that the principal ingredient used 

 by the ancient Egyptians in the formation of mummies was nothing 

 more than the vegetable tar of those countries, which is called by the 

 Arabs Katren. My first trials to prove the truth of this conjecture 



* Litre equals 0.220097 parts of British imperial gallon. 



