200 ANNUAL OF SCIENTIFIC DISCOVERY. 



lead. Hence may be inferred the freedom from corrosion of leaden 

 pipes connected with iron mains, so far as the reduction of the pul- 

 verulent peroxide of iron may influence it. (k) Alkaline chlorides 

 in natural waters deprived of air do not corrode lead. (i) Salts, 

 generally, impair the action of waters upon lead, by lessening their 

 solvent power for air, or for other salts. 



" A coat of greater or less permeability forms in all natural waters to 

 which lead is exposed. The first coat (/) is a simple suboxide absolutely 

 insoluble in water, and solutions of salts generally. This becomes con- 

 verted in some waters into a higher oxide, and this higher oxide, uniting 

 with water and carbonic acid, forms a coat (A;) soluble in from 7,000 to 

 10,000 times its weight of pure water. The above oxide unites with 

 sulphuric and other acids, which sometimes enter into the constitution 

 of the coat k ; uniting with organic matter and iron-rust, it forms 

 another coat (/) which is in the highest degree protective. The perfection 

 of this coat, and of the first above-mentioned, may be inferred from the 

 small quantity of lead found in Croton water (New York) after an expo- 

 sure in pipes of from twelve to thirty-six hours, and from the absence of an 

 appreciable quantity in Fairmount water (Philadelphia) after an exposure . 

 of thirty-six hours, when concentrated to one two-hundredth of its 

 bulk." 



ANALYSIS OF THE WATERS OF THE DEAD SEA. 



WE find in Poggendorff's Annalen an analysis of a quantity of water 

 from the Dead Sea, procured near the north end, not far from the mouth 

 of the Jordan. The water contains : 



Chloride of Calcium 2.894 



" Magnesium 10.543 



" Potassium 1.398 



" Sodium 6.578 



" Aluminum 0.018 



Bromide of Magnesium - - - - - - 0.251 



Sulphate of Lime 0.088 



Silica ... 0.003 



21.773 



ARSENIC IN CHALYBEATE SPRINGS. 



SINCE the discovery of arsenic in the deposits from certain chaly- 

 beate springs, it has been asked whether the poisonous properties of 

 this substance are not neutralized by the state in which it is found. 

 M. Lassaigne has finished a series of experiments connected with this 

 subject, for the purpose of ascertaining the proportion of arsenic con- 

 tained, in what state of combination it exists, and the nature of the 

 action which these arseniferous deposits exert on the animal economy. 

 The following are M. Lassaigne's conclusions : 1. In the natural de- 

 posits of the mineral waters of Wattviller. arsenic exists to the amount 

 of 2.8 per cent. 2. A portion of these deposits, representing 1.76gr. 

 of arsenic acid, or 1.1 4gr. of arsenic, produced no effect upon the 



