108 



CHEMISTRY. 



amount of nitrogen to decay, under circum- 

 stances in which all the nitrogen given off or 

 accumulated could be measured. The organic 

 matter consisted of dried and sifted barn-yard 

 manure, mixed with one-fourth its weight of 

 dried and pulverized flesh. The experiments 

 marked I. in the following tables were con- 

 ducted in purified air; those marked II. , in 

 purified nitrogen. The exposure to air in the 

 first set of experiments was kept up for more 

 than two months; the exposure to nitrogen 

 was for a shorter period ; the temperature 

 varied from 50 to 80, averaging 70 Fahr. 



The apparatus was exposed to diffused day- 

 light. 



QUANTITIES AND MATERIALS USED. 



KITEOGEX AFTER DECOMPOSITION (itf GBAMMES). 



These results show a loss of nitrogen in all cases 

 except 1 2 and II a ; the small gain of II } being with- 

 in the errors of experiment. The loss is ve.ry much 

 less in the second than in the first series of experi- 

 ments. This cannot be attributed to shorter dura- 

 tion, since the gain of II a is greater than that of I 2 . 

 It confirms the deductions of Lawes, Gilbert, and 

 Pugh t that the loss of nitrogen is caused by a process 

 of oxidation. Gypsum seems to prevent in part the 

 loss of nitrogen. The relation ot the formation of 

 ammonia to the experiments is not obvious. A con- 

 siderable gain of nitrogen is eifected in the experi- 

 ments where potash alone is mixed with organic mat- 

 ter. No trace of nitric acid was found, and there is 

 no reason to suppose it was formed during the ex- 

 periments. The gain of nitrogen cannot be ascribed 

 to nitrification. The fact of the fixation of nitrogen 

 is demonstrated ; the method is as yet open to ques- 

 tion. The following conclusions sum up our present 

 knowledge . 1. The loss of free nitrogen during the 

 decomposition of nitrogenous organic matter is gen- 

 erally due to oxidizing action. 2. An increase of 

 combined nitrogen in soil may take place by oxida- 

 tion of free nitrogen to nitric acid. 3. Some organic 

 substances in the presence of caustic alkali are able 

 to fix free nitrogen without the agency of oxygen or 

 the formation of nitric acid. 



Estimation of Nitrates in Potable Water. 

 A method for the estimation of nitrates in 

 potable waters, presented by Mr. W. F. Donkin, 

 of the British Chemical Society, is worthy of 

 note, as affording a ready means of ascertain- 

 ing the purity of water. A nitrate, in the 

 presence of chlorides, when treated with phe- 

 nol and sulphuric acid, gives a reddish solution 

 which, on the addition of an excess of ammo- 

 nia, changes to a more or less decided blue. 

 On this reaction the process depends. The 

 water under examination is compared with a 

 standard solution of potassium nitrate contain- 

 ing a known quantity of the salt ; these are 

 treated in a precisely similar manner. The 

 process is capable of accurately determining 



the amount of nitrates present to within one 

 part in four million parts of water. 



Proportion of Carbonic Acid in the Air. 

 The amount of carbonic acid in the atmosphere 

 has been newly investigated by Truchot. In 

 a communication to the Paris Academic des 

 Sciences he says that his method of analysis 

 consisted in passing a known volume of air 

 through a graduated solution of barium hy- 

 drate, allowing the barium carbonate to be 

 precipitated, and then re-titrating the solution. 

 His results are as follows: 1. At Clermont- 

 Ferrand (where he made his experiments) the 

 amount of carbonic acid in the air is greater at 

 night than during the day. 2. The proportion 

 is not sensibly greater in the city than in the 

 country. 3. In the vicinity of green-leaved 

 plants the proportion of carbonic acid varies 

 considerably, according as the green parts of 

 the plants are exposed to the direct solar rays 

 or to diffused light, or exist in the shade, 

 the amounts for these cases respectively being 

 3.54, 4.15, and 6.49 per 10,000 parts of air. 

 4. The mean amount of carbonic acid in the 

 air is 4.09 parts per 10,000. 5. This propor- 

 tion of carbonic acid bears an inverse ratio to 

 the altitude ; thus at Clermont-Ferrand (alti- 

 tude 395 metres) it is 3.13 ; on the Puy-de- 

 D6me '(altitude 1,446 metres), 2.03 ; on the 

 Pic de Sancy (altitude 1,881 metres), 1.72 per 

 10,000 volumes of air. 



Composition of Cosmic Dust. The Norwe- 

 gian explorer Nordenskiold on many occa- 

 sions discovered on the snow in high northern 

 latitudes minute particles of a black substance 

 to which he gave the name of cryoconite. 

 Since his return from the polar regions he has 

 analyzed this dust, comparing it with a sub- 

 stance of the same nature found by his brother 



