MARINE LIGHTING EQUIPMENT OF THE PANAMA CANAL. 



105 



is the most common size, being tested to 75 atmospheres), and completely 

 filled with the porous mass, a solid material possessing a porosity of 80 per 

 cent. That is to say, although the cylinder is apparently filled quite full, 

 only 20 per cent of the space is really occupied by the solid body, the remain- 

 ing 80 per cent being available for holding the liquid. Half of this remaining 

 space is occupied by acetone, which soaks into every pore of the porous 

 substance; the other half, or 40 per cent of the original volume of the 

 cylinder, is thus available for the expansion of the liquid. The cylinder is 

 closed by a reliable valve, through which the gas is pumped into the accumu- 

 lator, and through which it flows out again when required for service. 



As the acetone charge is equal to 40 per cent of the original volume of 

 the cylinder, and the solvent capacity of acetone is 25 times its own volume 

 per atmosphere of pressure, the acetylene storing capacity of the accumu- 

 lator is, accordingly, 10 times its own volume for each atmosphere. There- 

 fore, at a pressure of 10 atmospheres an accumulator contains 100 times its 

 own volume of acetylene; at 12 atmospheres 120 times, and so on; this being 

 computed for a temperature of 15° C. (59° F.) . The influence due to increase 

 or decrease in temperature will be noted further on. 



Accumulators are made in several standard sizes to suit different require- 

 ments. The three principal sizes used in this country for lighthouse work 

 are designated A-25, A-50, AW-300, the index figure denoting the volume of 

 the steel cylinder in liters, when empty (see Plate 48). 



Table of Accumulators. 



It will be observed from the above table that at 10 atmospheres pressure 

 an accumulator stores about one cubic foot of acetylene per ij pounds of 

 its weight. 



The greatest care must be taken at every step in the manufacture of 

 these accumulators. 



