Maech 14, 19U2. J 



SCIENCE. 



435 



capacity and resistance indicate that there can 

 be no coating of badly conducting oxid on the 

 iron, as has been assumed by some observers. 

 The conclusion is drawn that the surface of 

 passive iron consists solely of trivalent iron, 

 the formation of passive iron by oxidizing 

 agents and by electrolysis being due to the 

 replacement of bivalent by trivalent iron. 



The subject of the action of water upon 

 metallic lead is one that has been much stud- 

 ied, and the results of different observers have 

 been by no means concordant. A recent 

 extended investigation by Stanislav Ruzicka 

 furnishes results which are not wholly in 

 accordance with the generally received ideas. 

 His method was to place bright lead in cylin- 

 ders containing various solutions, insert a 

 stopper and leave the whole for twenty-four 

 hours. The amount of lead in the solution 

 was then estimated. Care was taken to ensure 

 the absence of air. Nitrates, chlorids, sulfates 

 and carbonates of alkalies and alkaline earths 

 were studied, and also various organic sub- 

 stances. Among his conclusions are the fol- 

 lowing: The action of salts is wholly inde- 

 pendent of the base, and is proportionate to 

 the solubility of the lead salt of the acid of the 

 salt used. Thus nitrates have the most action, 

 chlorids next, sulfates next and carbonates 

 least. The action of the first-mentioned salts 

 is diminished by the presence of carbonates in 

 the water, while the addition of a nitrate 

 increases the action of other salts. If the same 

 piece of lead is exposed to fresh solutions of 

 the carbonate, the action is much diminished, 

 and the same diminution occurs even in the 

 presence of nitrates and free oxygen. Free 

 carbon dioxid greatly diminishes the action of 

 water or salt solutions on lead, while air in 

 all cases increases it. Infusions of grass 

 leaves diminish the action of water, while it 

 is greatly increased by infusion of peat. 



A RECENT number of the Mineralogical Mag- 

 azine contains a jDaper by J. W. Evans on the 

 action of ground-water on pyrites, a study 

 called forth by the building of a reservoir in 

 northern llysore. It was feared that the large 

 quantity of pyrites in the underlying rock 

 would act harmfully on the water. It was 



found that when the water was free from car- 

 bonates the pyrites are very slowly acted on 

 with the formation of iron sulfate. On the 

 other hand, when carbonates are present iron 

 carbonate, hydroxids and oxids are to be 

 expected, the hydrates being first formed. 

 Free carbon dioxid in the water seems to be 

 without effect. In the presence of pure water, 

 metallic arsenids are changed into arsenates, 

 which are generally insoluble, and the pres- 

 ence of carbonates has merely the effect of 

 retarding the change. 



In an examination of Oriental medicines, P. 

 Guigues had occasion to test a sample of 

 'Zerquoun minium,' which is used as a rather 

 expensive substitute for the red oxid of mer- 

 cury. The specimen resembled red lead, but 

 had a lower specific gravity. On treatment 

 with water a white sediment and a red solu- 

 tion were obtained. The former proved to be 

 a magnesium silicate and the red substance a 

 coal-tar dye, revealing the fact that adultera- 

 tions are not peculiar to the Occident. 



The above recalls the fact that the writer 

 came into the possession some years ago of a 

 specimen of Chinese medicine held in high 

 esteem, which, it was supposed, was prepared 

 from urine by some intricate method. Exam- 

 ination showed it to be ordinary salt, and of 

 so pure a quality that it was hardly conceiv- 

 able that it had been prepared from its reputed 

 source. 



J. L. H. 



CURRENT NOTES ON METEOROLOGY. 



MAURITIUS METEOROLOGICAL SOCIETY. 



It is a pleasure to note that the Meteorolog- 

 ical Society of Mauritius has taken a new 

 lease on life. This Society, with which the 

 late Dr. Charles Meldrum was so closely asso- 

 ciated, has in the past been active in promot- 

 ing a study of the cyclones of the South 

 Indian Ocean, to which study Meldrum 

 devoted a large share of his time for about 

 forty years. The successor of Dr. Meldrum as 

 director of the Royal Alfred Observatory and 

 also as secretary of the Meteorological Society 

 of Mauritius, is Mr. T. F. Claxton, F.E.A.S., 

 who is evidently doing much to arouse inter- 



