Intelligence and Miscellaneous Articles. 153 



ON LIQUID PROTOXIDE OF NITIIOGEN. BY M. DUMAS. 



M. Natterer of Vienna has constructed a forcing-purap for the 

 liquefaction of gases, by means of which carbonic acid and protoxide 

 of nitrogen can readily be obtained in the liquid state. Having 

 procured one of these instruments, and employed it more especially 

 for the liquefaction of the protoxide of nitrogen, I soon perceived 

 the necessity of using a series of indispensable precautions, but 

 which, once adopted, have enabled me to effect with promptitude 

 and security, as well as oeconomy, the liquefaction of large quantities 

 of protoxide of nitrogen. 



As this liquid furnishes a means of producing an excessively low 

 temperature, and is very easily operated with, I will here briefly 

 point out the observations I have made. The first relates to the 

 principal piece of the apparatus, that is to say the reservoir. In 

 my opinion the Viennese manufacturer has not given it sufficient 

 strength. I have had it surrounded with a belt of forged iron, 

 capable of resisting 800 atmospheres, and very nicely made by 

 M. Bianchi. Moreover, I arranged things so that the reservoir 

 being surrounded by ice, the body of the pump was cooled un- 

 interruptedly by a circulation of water around it, and that even 

 the stem of the piston was always moistened by cold water; in 

 this manner there is no danger of the valve of the piston being 

 injured by the heat proceeding from the compressed gas, and by 

 its special action as a combustible gas. With these precautions, 

 we may compress into the reservoir in the course of two hours 200 

 litres of gas, of which 20 suffice to produce a pressure of 30 atmo- 

 spheres, about which liquefaction commences. The remainder of 

 the gas furnishes a liquid ; 100 litres yield 200 grms., or very nearly. 

 The gas should be absolutely dry in order to succeed, and likewise 

 as pure as possible. I prepare it from the nitrate of ammonia as 

 usual, and after having dried it, pass it into Macintosh bags ; a 

 couple of pounds of nitrate of ammonia suffices. 



Once compressed, the liquid gas may be preserved for one or two 

 days at least in the reservoir ; the valve however is slightly injured 

 by it. When the stopcock of the reservoir is opened, the gas 

 escapes ; a portion freezes at first, but it then flows liquid ; 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 by far the most abundant, and of which it is easy to obtain in one 

 operation 40 to 50 grras., being received in a glass, keeps for half 

 an hour, or even more, in the air. 



In order to observe more readily its properties, I collected it in 

 open tubes, contained in vessels at the bottom of which was placed 

 some pumice-stone moistened with sulphuric acid. It then retains 

 its transparency for a very long time. 



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

 perfectly transparent ; each drop that falls upon the skin produces 

 a very painful burn. The gas, which is incessantly liberated by a 

 slow ebullition, possesses all the properties of the protoxide of ni- 



