DISTILLED WATER. 



125 



The following description and figure of a distilled-water apparatus devised by 

 the author for use in the Laboratory of Plant Pathology, United States Department 

 of Agriculture, may be of interest, therefore, to some. The apparatus consists of a 

 galvanized-iron boiler similar to those used in kitchen ranges. It is 1 8 inches in 

 diameter and about 5 feet high. The top is sawed off and to it is bolted a stout 

 iron ring with a flange, on which rests a ^-inch brass cover. In the lower half of 

 this boiler is a coil of 52 feet of inch copper pipe, the upper end bent downward 

 and securely fastened in the bottom of the boiler to a steam pipe (i inch) connected 

 with a i ^4 -inch steam pipe leading to the ordinary steam boiler in the engine room 

 in the basement; the lower end connected with an iron steam pipe (i inch) leading 

 to a steam trap (Mark traps are said to be the best). Around this copper steam 



pipe, which is of course tin- 

 plated, stands the river water 

 which is to be converted into 

 steam by contact with the hot 

 pipe. This hydrant water is 

 kept always at about the same 

 level (level of fig. 5 in plate 14), 

 by means of a tinned-copper ball 

 float (automatic cut-off) which 

 closes the mouth of the inflow 

 pipe when the water rises be- 

 yond a certain point. The upper 

 part of the cylinder is a steam 

 chamber under very moderate 

 pressure (o to ^ pound, rarely 

 more). The excess of pressure 

 is dissipated either by escape of 

 steam through the safety valve 

 (9), which is not weighted, or 

 through the coil of pipe in the 

 condenser. The steam passes 

 from a securely riveted tin-lined 



copper catch basin (8) into a ^-inch block-tin pipe (10), which is fastened to a 

 tubular projection from the catch basin by means of a collar screw. The tubular 

 projection from the top of the catch basin is soldered in place and also held by a 

 flange inside the copper top, so that it can not be forced out by any attainable 

 degree of steam pressure. The J^-inch block-tin pipe passes to the room above, 

 where it is coiled for a length of 35 feet inside a tin-lined copper tank resting on 

 the floor. The height of the condensing tank is 18 inches and its diameter is the 

 same. When in operation this tank is full of running water. Theoretically, this 

 condensation tank is large enough, and it is so practically when the hydrant pressure 



*Fic. 117. Detail from fig. 115 at B, showing an early stage of water-pore infection of cabbage. 

 The bacteria have not yet entered the spiral vessels. The large dark bodies are nuclei. 



