RESEAKCHES UPOIsr THE CHEIVHCAL PROPERTIES OF GASES. 



207 



the gas was found to exert a slight reducing action upon palladium chloride solution. 

 The compounds of nitrogen result usually by indirect processes from other com- 

 pounds. Additive reactions are rare. 



Some interesting cases of direct union of nitrogen have been discovered by 

 Merz (Ber., 1891, p. 3942), who has shown that magnesium heated to redness in 

 nitrogen produces a nitride. The nitride so formed is stable in dry air, but yields 

 magnesium hydrate and ammonia in presence of moisture. So great is the affinity 

 of magnesium for nitrogen that, on burning in moist air, the same compound results. 

 The oxide formed always contains ammonia as a decomposition product of this 

 nitride (Aslonoglow, Chem. News, LXII, p. 99). The combination of nitrogen and 

 magnesium could only prove of interest as a gas reaction in case the formation of 

 the compound is not interfered with by the presence of such gases as are not readily 

 removable from a mixture. Sulphur and oxygen compounds would naturally be 

 decomposed by magnesium. 



In experiments with natural gas, as supplied to Allegheny, in October, 1892, it 

 was found that magnesium heated to redness in a stream of the gas for one-half 

 hour yielded a strong odor and the usual reactions characteristic of ammonia on 

 moistening. The compound produced exhaled ammonia on exposure to air. Nitro- 

 gen also unites directly with lithium and potassium. 



Ouvard (Compt. Bend., CXII, p. 120) obtained a nitride of lithium containing 

 50.28 per cent, of nitrogen. 



OXTGElSr. 



Reactions. 



The presence of oxygen in very small quantities in a gas mixture is easily 

 recognized by the change of color produced in a precipitate of ferrous ferrocyanide 

 or manganous hydroxide, or in a solution of pyrogallol in soda, or indigo solution 

 previously bleached by zinc dust. All of these substances absorb oxygen and at 

 the same time undergo a change of color. The most sensitive of these is the mix- 

 ture of pyrogallol and alkali. A very sensitive reagent for fi'ee oxygen is found in 

 precipitated manganous hydroxide in water, which, by reason of very complete 

 oxygen absorption, changes into MujOo, its color changing at the same time from 

 white to brown. The following process is a modification of Winkler's method for 

 the determination of dissolved oxygen in water {Zeitschr. Ang. Chem., 1891, p. 105). 



Two bottles of about two ounces capacity are connected as shown in the sketch. 

 The gas stream enters by A and bubbles through soda solution and manganous 

 chloride consecutively. After complete expulsion of air by the gas current, the 



