I.KSSONS IN rilKMISTHY. 



UKSSON8 IN CHEMISTRY. X. 



LOWER OXIDES OF NITKOOEN AND COMPOUNDS O. 



GAS WITH HYliK" 



TUB protoxide qf nitrogen, nitrout oxide, or lauyhin<j gat (NiO, 

 weight- 44 ; density, because it in a compound ga,- 



1 by heating in a flask ammonium nitrate; the 



: melts, and by slightly raising and continuing the boat 



ib becomes decomposed, resolving itself into mtroun oxide and 



, wuter, wkiuh comoa away aa stoain. This in expressed thug : 



The gas cannot bo colleotod over cold water unless with much 

 loss, for 100 cubic incites of water at 13 Cent, absorb 77 of the 

 gas. However, if the water bo hot, a very small quantity is re- 

 tained, hence the gas must be collected over hot water or mer- 

 cury, upon which metal it has no action. 



1'roperiies. The gas is colourless and without smell, but 

 possesses a sweetish taste. 



When subjected to a pressure of about 30 atmospheres at the 

 temperature of Cent, by a process which will bo described in 

 a succeeding lesson, the gas becomes a clear liquid. The 

 same phenomenon is exhibited if the gas be cooled down to 

 88 Cent., that is to say, liquid nitrous oxide boils at 88, or 

 the vapour of that liquid (that, is nitrous oxide gas) has a tension 

 equal to one atmosphere at the temperature of 88 Cent.; and 

 as it requires a pressure of 30 atmospheres at Cent, to liquefy 

 it, we say that at Cent, the gas has a tension of 30 atmo- 

 spheres. When liquid nitrous oxide is mixed with bisulphide of 

 carbon, and caused rapidly to evaporate under the exhausted 

 receiver of an air-pump, the greatest known degree of cold is 

 obtained -140 Cent. 



When a body in a state of ignition is plunged into this gas, the 

 gas is decomposed into nitrogen and oxygen, this latter causing 

 the body to burn with the same brilliance aa if it were in pure 

 oxygen. With sulphur the process is somewhat peculiar : if the 

 sulphur be only ignited feebly, the flame will be extinguished, 

 showing that there is some effort required to determine the 

 decomposition of the gas ; therefore the sulphur must be in a 

 state of thorough ignition. 



The resulting compounds are exactly those in the cases 

 alluded to in the lesson on oxygen. 



If the experiment of burning phosphorus in this gas bo 

 arranged as in Fig. 34 that is, a jar of the gas over water, 

 the stopper of the jar being rapidly removed, and in its place a 

 cork fitted, through which is passed a " deflagrating spoon," in 

 which is a piece of ignited phosphorus it will be observed 

 that the water in the jar will have 

 no tendency to rise; whereas if 

 the gas had been oxygen instead 

 of nitrous oxide, as the phospho- 

 rus consumed the oxygen, of course 

 the water would rise to fill the 

 place of the gas. The explanation 

 of this fact is, that in nitrous oxide 

 there is as large a volume of nitro- 

 gen as of the compound gas, that 

 is, in two volumes of the gas there 

 are two volumes of nitrogen and 

 jij ^ one volume of oxygen, these three 



volumes being condensed into 

 two. The combination of gases by volume offers no difficulty 

 if the student remember that simple gases are reckoned as 

 one and compound gases as two volumes. To illustrate this 

 statement 



5N,O + 2P = P,O, + ION 



represents the process which takes place when phosphorus is 

 burnt in nitrous oxide. The P 9 O 8 (phosphoric acid), which i.s 

 formed, being a solid, does not enter into our calculations of the 

 volumes of the gases ; but it will be observed that there arc five 

 atoms of a compound gas (NjO), and on the other side of the 

 equation ten atoms of the simple gas N : hence, according to the 

 above statement, if wo reckon the compound gas as two volumes, 

 we shall have ten volumes of N,O, and after the combustion has 

 taken place we shall still have an equal quantity (ten volumes] 

 of gas left namely, ten volumes of the simple gas N, which is 

 rerified by the experiment. 



45 N.E. 



To give another example : carbonic oxide burns with oxygen 

 bo form carbonic acid gau, thus : 



CO + O CO,. 

 2 + 1 - 1 



The figures represent the volumes, that is, two volume* of CO 

 [carbonic oxide) and one volume of oxygen combine to form two 

 volumes of CO, (carbonic acid). We nhall find that ammonia U 

 separated into its component gases, nitrogen and hydrogen, 

 under certain circumstances, or as thus expressed : 



NH, N + 3H. 



2=1 +3; 



or two volumes of ammonia when decomposed become on* 

 volume of nitrogen and three of hydrogen, or four volume* of 

 the constituent gases, in combining to form ammonia, condeoM 

 into two volumes. Wo shall 

 often meet with illustra- 

 tions of this simple rule. 



There is a more delicate 



method of demonstrating ^ ^^ __ 



the composition of nitrous ' \ 



oxide. The bent tube in 



Fig. 35 is filled with mer- Fig. 35. 



cury , a small piece of potas- 

 sium having been introduced into the bent part by an iron wire; 

 the tube is inverted into a capsule of mercury, and nitrons oxide 

 gas passed into it. Heat is then applied to the potassium, the 

 end of the tube beneath the mercury being covered by the finger 

 to prevent the escape of tho gas when combustion takes place. 

 The potassium takes the oxygen from tho gas, forming potash, 

 and the nitrogen is left. After the combustion is perfected, the 

 finger may be removed, and it will bo found that the mercury 

 stands at the same point in the tube, thus proving that although 

 the oxygen has been abstracted, it retains its original volume. 



The most remarkable property of nitrous oxide, and from 

 which it takes the name of "laughing gas," remains to be 

 mentioned. It may be inhaled from an india-rubber bag. Place 

 the tube from tho bag in the month, close the nostrils, and 

 breathe the gas in the bag. After about 2} minutes a pleasur- 

 able sensation will be experienced, which expresses itself in 

 uncontrolled fits of laughter, or it may be exhibited in muscular 

 exertion, which, if the subject be strong, amounts to "dangerous." 

 There is little or no danger in this experiment to the majority 

 of persons ; but where the heart is diseased, or in persons of 

 full habit, it had better not be attempted. Within the last 

 few months the pure gas, unmixed with air, has displaced 

 chloroform in minor operations, especially in dentistry. The 

 patient breathes the gas and becomes unconscious and insensible 

 to pain. The effect lasts a minute, or a little longer. 



Nitric Oxide (N,O, = NO ; combining weight, 30 ; density, 15). 

 As the termination ic will indicate, this gas contains more 

 oxygen than nitrous oxide. It is easily obtained by acting OB 

 copper with nitric acid diluted with 2J times its volume of 

 water. The action is thus expressed : 



3Cu + 8HNO. = 3 (CuSNO.) + 4H.O + N,O,. 



The flask will be found full of red fumes, for nitric oxide com- 

 bines at once with oxygen to form nitric tetroxide, which is a 

 deep-coloured gas. This action is an infallible test for the 

 presence of nitric oxide. The gas may be collected in the 

 usual way over water, and it will be found to bo colourless. It 

 is less ready to support combustion than nitrous oxide, seeing 

 that it requires a greater heat to decompose it, so that it* 

 oxygon may take part in tho combustion. Phosphorus, when 

 immersed in this gas, must be very thoroughly ignited, or it will 

 be extinguished. Pelouze suggests tho following manner for 

 procuring this gas perfectly pure : Digest hydrochloric acid 

 with iron filings till it will dissolve no more ; decant that is, 

 pour off the clear 'liquid, and add to it its own bulk of hydro* 

 chloric acid. Place the liquid in a retort, and add potassium 

 nitrate (saltpetre), and the nitric oxide begins to come off in 

 large quantities. The composition of the gas may be deter- 

 mined as in the case of nitric oxide. If the formula be N.O,, 

 it will be evident that we must have as much nitrogen left after 

 tho combustion as there was nitric oxide before. Thus : 

 N.O, == 2N + 20. 

 8=2+3. 



The oxygen, being in solid state in the potash, is not taken ur.o 



