TRANSACTIONS OF THE SECTIONS. 67 



On the Examination of Water for Sanitary purposes. By Gustat Bischof. 



The principle of the method consists in evaporating 1 cub. centim. of the ^vater 

 to he examined in a cell formed by cementing a glass ring on a slip of plate glass, 

 such as used for mounting microscopic objects. By means of certain appliances 

 dust is effectually excluded during the evaporation. The temperatm-e at which 

 the samples are evaporated (40° to 45° C.) is regulated by a Kemp-Bimsen gas- 

 regulator improved for the puiijose by the author. 



If pure water, such as we find naturally, be evaporated, one observes imder the 

 microscope in the residue essentially colomiess, or nearly colom-less, dendi-itic, 

 branching, tree-like, and well-detined hexagonal and rhombohedi-al crystals of 

 calcium carbonate. In the case of natural impure water, or if pui'e water be 

 contaminated by adding minute quantities of either sewage or urine, the above 

 crystals are no longer perceptible, and, according to the degi-ee of impurity, their 

 place is taken by more or less imperfectly defined yeUowish-brown or red hexagonal 

 or rhombohedral crystals of calcium carbonate, or by hexagonal twin-crystals, or 

 triangles with rounded angles, or, finally, drops of fat and the so-called dumb-bella 

 (which latter are either fatty matter or germs of fungi) make their appearance. 

 _ If the presence of germs of fungi be doubtful, they are determined by cultiva- 

 ting tlie residue in a damp chamber for some forty-eight hours before'it is quite 

 evaporated to dryness. Several well-definable species of fungi have thus been 

 produced. 



_ The results of the examination of a number of samples, illustrated by several 

 lithographed plates, proved that one-thousandth part of sewage or mine added to 

 pure water so completely altered the appearance of the residue as to lead to the 

 conclusion that still more minute quantities of the above impmities can also be 

 detected in water by this method. 



On the other hand, the residue of sewage which had been filtered through 

 spongy ii-on (the process to which the author called attention at the last Meeting 

 of the Association) exhibited throughout the characteristics of the purest water. 

 Professor Voelcker anived also, by chemical analysis, at the residt that the 

 sewage filtered through spongy iron was " remarkably free from organic matter, 

 containing less organic matter than many excellent drinking-waters," thus proving 

 that analysis and the microscopic examination come to the same conclusion. 



In concluding, some residues of natural waters exhibited in the plates referred 

 to above were explained as to their characteristics. 



On the Crystallization of Metals hy Electricity . By Philip Beaham. 



The author of this paper gave an accouut of experiments with electricity under 

 the microscope. Solutions of neutral metallic salts were placed between temiiuals 

 of the base, and crystals of several metals were formed. The author hopes by the 

 same means to obtain crystals of all. 



The apparatus for regulating the quantity and intensity of the electricity was 

 exhibited and explained. 



The author then drew attention to the shape of the crystals, and suggested that, 

 being built up of molecules^ they might be typical of their elementary forms, 



On the Bate of Action of Caustic Soda on a watery Solution of Chloracetic 

 Acid at 100° C. By J. T. Btjchaitak. 



Two setsef experiments were made. In the one, the composition of the solu- 

 tion was expressed by the formula C,H3C102-t-NaII04-159H^O,j^n the- other by 

 CaHgClO^+SNaHO + loDH ; 10 cub. centims. of tha difl«rent solutions were 

 iised for every experiment. The results are given iu the following Tables : — 



