T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
52
beads or rods are used, yet absorption is as rapid as with either. These pipettes may be made by any good glass blower, or they may be obtained for about $ j . o o each from Mr. Paul Anders, Urbana, Illinois. COLLEGE O F AGRICULTURE os ILLINOIS UNIVERSITY URBANA,ILLINOIS
NEW REFLUX CONDENSER By JAMESJ. BAJDA Received July 10, 1918
A modified type of reflux condenser, applicable t o most kinds of laboratory work, has been found very satisfactory, especially in those cases in which t h e refluxing liquid has a comparatively high boiling point. I n t h e usual type of reflux condenser, hot vapors enter the relatively cold portion of the cooling chamber and allow the condensed liquid t o collect in t h e inner tube, until overbalancing pressures therein cause t h e liquid t o spurt back into t h e receiver. This spurting back is often not very desirable, especially as the receivers are usually made of glass. The improvement here is obvious from the accompanying drawing and consists of a vapor conduit, 2 , forming a part of t h e adapter of the condenser I , through which t h e vapors pass and are led therefrom into the upper part of the condensing coil 3. The condensate flows into the t r a p 4, b y means of which is provided regular and undisturbed flow into the receiver. Any tendency t o disturb t h e balanced relation of the condensed liquid in t h e t r a p will find outlet through one arm of t h e Y-tube which leads upwardly and axially, 5, through t h e cooling coil 6. The flow of c o o h g water in a direction opposite t o t h a t of t h e condensates diminishes the strain on t h e glass.
/,
FLUSHING, I,. I. N E W YORK
Vol.
11,
No.
I
MELTING POINT OF ROSIN BY T. LINSEY CROSSLEY Received August 2, 1918
Certain large buyers of rosin have recently specified a melting point limit for this material. Samples have been submitted for this test, b u t without specifying how t h e test was t o be carried out. Properly speaking, rosin, like asphalt, has no definite melting point, therefore, any specification aiming t o grade it by reference t o its behavior on heating should state t h e method for obtaining results. Schwalbe and Kuderlingl not only state melting points but record results t o fractions of one degree and claim t o differentiate between certain rosins b y their melting points. Several methods have been used t o determine t h e quality of rosin as indicated b y its action on heating. The closed capillary tube, of such general application, is used largely but, unless conditions of heating and observation are closely controlled, results are not uniform with different operators. The following results were obtained on t h e same four samples b y methods indicated: Rosin 1..
..........
2
............
3
............
4......
......
1/4 in. Column F. 174-184 172-183
l/s in. Column
F.
176-187 174-185
169-172 169-172 165-173 174-182 167-176
161-167 161-157
149-15 1 145-146
...
...
...
.
.
I
...
153-155 145-147 147-155 144-145 149- 153 Heated until clear. Probably mechanical weakness of film.
...
(a
(b]
Film
F.
150 146
...
147 155 156 120(b) 134 126 135 133
...
Capillary F. 146 145 154(a) 154 147 153 128 130
...
138 136
...
The first three methods were carried out as follows: Glass tubes of about S/le in. inside diameter and 2 in. long were prepared. These were dipped in melted rosin so t h a t on cooling there was left inside t h e t u b e a column of rosin of the required depth. I n t h e case of t h e method marked “Film” t h e foot of t h e glass tube was heated slightly and applied carefully t o t h e surface of t h e molten rosin so t h a t upon cooling a thin film only of t h e rosin was formed. The tubes were attached to the thermometer in such a way t h a t t h e bottom of t h e tube with t h e rosin was located about t h e center of t h e mercury bulb. The thermometer with tube attached was immersed in cold water in a 400 cc. beaker with t h e bottom of t h e rosin column I in. below t h e surface. The temperature was raised about 3’ per minute. I n t h e cases of 1/4 in. and in. columns, it will be noted t h a t two temperatures are given. The lower temperature indicates t h e point a t which the rosin is soft enough for t h e water t o enter t h e tube, t h e other being the point a t which t h e water breaks through. The result is of course merely t h e point a t which t h e viscosity is so reduced t h a t it is overcome b y t h e pressure of I in. of water. It is necessary t h a t t h e heating should be well regulated. If heat is applied too rapidly it will naturally result in a higher final temperature and a wider spread between t h e two points. 1
“Rosin Studies,” J. SOC.Chem. Ind., SO, 1397.
