CHEMISTRY. 



125 



thirty-six to forty-eight hours. In practice M. 

 Livache takes an ordinary lead-oil, adds dry 

 manganese sulphate in fine powder, and agi- 

 tates for some time in the cold. The manganese 

 is entirely substituted for the lead, and the oil 

 obtained, free from dregs by simple decanta- 

 tion, possesses an extreme drying power. 



Domestic Chemistry. The water supplied to 

 Cwmfelin, Wales, after being carried half a 

 mile through a galvanized iron pipe, was 

 found to have absorbed 6*41 grains of zinc 

 per gallon, the water at the spring being 

 free from that element. Mr. 0. W. Heaton 

 has confirmed the analysis by an experiment 

 that showed water capable, with the aid of 

 oxygen and carbonic acid, of dissolving zinc 

 immersed in it. The subject of the solution of 

 zinc by water in contact with it, was discussed 

 by Thomas Stevenson in the " Guy's Hospital 

 Reports for 1872." Dr. Stevenson there stated 

 that, having been employed to arrange the 

 water-supply for a private house, he ordered 

 the rain-water from the slate -covered premises 

 to be brought in through iron pipes. Contrary 

 to his instructions, galvanized pipes were used, 

 and the water that came through them was 

 observed, after several weeks, to be turbid and 

 milky, and was found to contain a notable 

 quantity of zinc in suspension, and some in 

 solution. It is pointed out, in the "Sixth Re- 

 port of the Rivers' Pollution Commission," 

 that certain polluted, shallow well-waters, con- 

 taining much dissolved oxygen, and but little 

 carbonic acid, possess the property of acting 

 continuously on both bright and tarnished 

 lead, and that, when galvanized iron pipes are 

 used, the water is impregnated with zinc in- 

 stead of lead. The water of Loch Katrine, 

 which acts on both bright and tarnished lead, 

 also attacks galvanized iron. The presence of 

 zinc in water is easily recognizable by the thin 

 white film which forms on the surface of the 

 water when the latter is exposed to the air. 

 Dr. Stevenson remarks that zinc in solution in 

 potable waters is best detected by the addition 

 of potassic ferrocyanide to the clear water 

 after acidulation with hydrochloric acid. A 

 whitish cloud will immediately form if zinc be 

 present. 



F. P. Venables, Ph. D., of the University of 

 North Carolina, relates an instance of zinc-im- 

 pregnated water which came under his obser- 

 vation. The water was brought by galvanized 

 iron pipes, and stored in a zinc-lined tank 

 painted with white-lead. It became somewhat 

 turbid and metallic-tasting, and its use for 

 drinking purposes was discontinued. On anal- 

 ysis, the water in the tank was found to con- 

 tain 4*48 grains of zinc carbonate per gallon, 

 with a trace of iron, and no lead. Water from 

 the pipe gave 4'29 grains of zinc carbonate per 

 gallon, and a trace of iron. 



Seeking to determine the conditions under 

 which the soap-test for hard water fails, Mr. 

 Herbert Jackson found that the presence in 

 solution of the salts of either calcium or 



magnesium, in quantities sufficient to give 23 

 of hardness on Clark's scale, invalidated the 

 test. In the case of waters containing the 

 salts of both metals, if the salts of mag- 

 nesium were in solution in quantities suffi- 

 cient to give more than 10 of hardness, no 

 evidence could be obtained of their presence 

 so long as the salts of calcium in the same 

 water exceeded 6; in such a case, a perfect 

 and permanent lather was produced when 

 soap had been added equivalent to 7 of 

 hardness. Reliable results were obtained on 

 diluting the water so as to reduce the propor- 

 tions of the salts below those stated above. 

 When the water was heated to 70 C., a com- 

 plete reaction was caused between the soap 

 and the salts. With one of the constituents of 

 the soap, sodium oleate, perfectly trustworthy 

 results were obtained in very hard waters 

 without either diluting or heating. 



The water of the river Oder above Brelau, 

 in its course through the city, and for fourteen 

 kilometres, or about ten miles, below the town, 

 has been examined by Franz Hulna to deter- 

 mine the effect of sewage upon its purity. 

 From the point where the water-supply of 

 Breslau is pumped up, to a little above the 

 town, the water undergoes a slight but appre- 

 ciable deterioration, but after filtration is quite 

 suitable for domestic uses. In passing through 

 the city, a continuous change for the worse 

 takes place, which is manifested by the in- 

 crease of oxidizable matter and of chlorine, 

 and by a hundred-fold augmentation of am- 

 monia and albuminoid ammonia. Microscopic 

 examination disclosed the abundant presence 

 of organisms of putrefaction. Farther down 

 was observed a gradual process of self -purifica- 

 tion by contact with oxygen, along with the 

 cooperation of vegetable and animal life in the 

 stream. Ten miles below the city the influ- 

 ence of sewage could not be detected either by 

 chemical or microscopic examination. 



According to the statements of Prof. Petten- 

 kofer, at the Hygienic Congress in Berlin, the 

 poisonous effects produced by coal-gas are de- 

 pendent upon the presence of carbonic oxide 

 in the proportion of about ten per cent., while 

 the other constituents of the gas, although ir- 

 respirable, do not act as direct poisons. The 

 danger in breathing the gas does not depend 

 so much upon the duration of the exposure to 

 a mixture of air and carbonic oxide, as upon 

 the amount of the latter contained in the air. 

 Air containing only y^TS- of carbonic oxide 

 can be breathed for a considerable time with- 

 out injury to health ; a proportion of seven or 

 eight to 10,000 causes appreciable discomfort; 

 of twenty to 10,000, difficulty of breathing, 

 weakness, and uncertainty of gait ; a propor- 

 tion of twice that ratio leads to stupefaction ; 

 and higher proportions to extreme and fatal 

 effects referable to the nervous system. Gas- 

 sickness increases in the winter months, large- 

 ly, probably, because the rooms are closed and 

 the gas is drawn into them through the arti- 



