48 JOURNAL OF THE 



dipped in a bath of zinc and so superficially coated with it and to a 

 certain extent alloyed ^vith it. The character of the protection 

 afforded the iron is galvanic (hence the name), the two metals form- 

 ing a galvanic couple, so that under the action of any exciting liquid, 

 the zinc and not the iron is attached. That zinc dissolves in potable 

 waters h is long since been shown by the experiments of Boutigny, 

 Schaueifele and Langonr^e. Distilled water and rain water dissolve 

 it more readily than hard water. Especially is water containing 

 carbonic acid capable of this solvent actior. So much may be taken 

 up that the water becomes opalescent and acquires a distinctly me- 

 tallic taste. It seems that by the action of water, hydrate and car- 

 bonate of zinc are gradually formed, and that this action is more 

 rapid in the presence of certain saline matters, but is weakened by 

 the presence of calcium salts. 



As to the injurious effect of such waters, authorities differ. Fons- 

 sagrives has investigated the question, consulting the statistics of 

 the French Navy and the recorded experiments of other, adding, 

 however, none of his own. The French Government had, before 

 this, appointed a committee to make a special report on the subject, 

 and the investigations of Roux in 1865 and 1866, furnished evidence 

 enough of possible injury to health from water stored in galvanized 

 iron tanks to lead to an order, from the Minister of Marine, prohib- 

 iting the use of such tanks on board of ships of war. Boutigny 

 attributed grave effects to the use of these zinc-containing waters, 

 looking upon it as probably resulting in epilepsy. Fonssagrives, 

 however, maintains that the zinc is not cumulative and produces no 

 bad effects unless taken in large doses. Doubt is thrown on this 

 position though by the fact that Ms assertions as to the limited solu- 

 bility of zinc in ordinary drinking water are not sustained by experi- 

 ments. Without doubt such waters have been used for considerable 

 lengths of time and no injurious effects have been noticed. This 

 may have been due, however, to the hardness of the water, and 

 hence the small amount of zinc dissolved. Pappenheim states 

 in contradiction to the assertion of Fonssagrives that zinc vessels 

 are dangerous and must be carefully avoided. Dr. Osborne, of 

 Bitterne, has frequently observed injurious effects from the use of 

 waters impregnated with zinc. Dr. Stevenson has noticed the sol- 

 vent action of rain-water on galvanized iron and states that proba- 

 bly its continued use would cause injury to health. He recommends 

 as a convenient test for the presence of zinc in potable w^aters, the 

 addition of potassium forocyanide to the filtered and acidulated 

 water. Zinc gives a faint white cloud or a heavier precipitate when 



