416 R. H. Richards—Jet Aspirator for Laboratories. 
was cut off at a (see fig. 5), and its lower extremity a was 
dipped into a large beaker full of water and the water poet 
turned on to determine the form in which the foam 
naturally arrange itself, It assumed the form of a paren mee 
with no observable curve. 
The angle of this cone was determined under quite a number 
of different pressures, to see if it would vary with the pressure. 
of measuring the angle was rough (sighting by two 
rulers and transferring 4 Pape but the angle does not seem 
to vary with the pressur 
Taste | 
T pressure, i 
mm. of mercury whisk Angle of 
would balance it. foam outline. 
2054 ¥ 
2054 172° 
2054 14 
1521 16° 
1275 16}° 
1103 143° 
892 pb es 
425 13° 
The exact condition of things in this aspirator seems to be 
that the water jet, on arriving at a, fig. 3, is obliged to fill the 
whole cross section at a, thus forming a wad or diaphragm 
which, if we trace in its forward movement to o, we shall find 
that this elementary portion of the jet must do one of two 
things in order that it shall fill the cross section at 0: it must 
either lose momentum or.it must take air with it to help it to 
fill up the space. Practically both these things take place. 
Sufficient reason has already been given for having the angle 
of this cone as large as possible (i. e., the elimination of friction 
and the most rapid reduction of momentum). 
The following experiment, however, was tried with a view 
to prove a points. An aspirator (fig. 6) was made, having 
a=oand w:a = 056”: 080”. The distance from a to 0 was 
varied by Tualling jet successively off: the length ao is 
noted under each — in the table. 
Air tension. 
5 2 inches. 0 * 
“ 932 cc 
3° oe Beko 
dg - s7E * 
This indicates that the shorter the constricted tube ao became, 
r was the result in exhaustion 
The experiment just described also distinctly shows that the 
me Aaptrtor must have a definite point assigned for the field of 
“2 eee 
