June,
I9I 7
THE: JOL7RiY,4L O F I N D G S T R I . 4 L AA'D E N G I N E E R I N G C H E M I S T R Y
We have used the mercury purified in this manner in our thermoregulators and found it t o give satisfactory results. Calomel half-cells made up with this mercury have checked closely with each other a n d with cells made Erom pure mercury obtained from t h e Bureau of Standards. An a t t e m p t was made by using Hulett's method' for determining small traces of impurities, t o distinguish between yarious stages of purification, b u t no clear-cut differences were obtained. BUREAUOF
CHEMISTRY, W A S H I N G T O N ,
D. C
HANDLING LABORATORY SOLUTIONS BY SUCTION By C L BEALS
Received February 10, 191;
To avoid lifting heavy bottles of solutions constantly employed in t h e laboratory, a n ordinary filter p u m p provided with a few simple rubber and glass connections may be used t o advantage. The accompanying illustration shows a n adaptation of t h e idea which has been successfully applied a t our laboratory for dilute acid a n d alkaline solutions used in fiber determinations. The cumbersome supply bottles are placed out of t h e way under t h e bench. Each is fitted with a a-hole stopper (one hole acting as a n air vent) through which a glass t u b e extends nearly t o the bottom of t h e bottle. These tubes are connected by means of 3/s-in. light pressure tubing t o short glass nipples likewise extending through 2-hole stoppers of a size suitable for t h e flask in use. Nipples passing through t h e other holes of t h e stoppers are similarly connected b y rubber tubing a n d a glass Y t o t h e filter
pump. For convenience, t h e tubes leading from t h e rubber stoppers are bound together for a short distance with adhesive tape. T o handle solutions, one has now only t o place t h e stopper connected with t h e desired solution tightly into t h e service flask and s t a r t the filter pump. A vacuum tends t o form in t h e syst e m , which is made complete b y closing one branch of t h e Y by pressure of t h e fingers a t a (or a' as t h e case may be). When sufficient solution has flowed into t h e service flask i t is instantly stopped b y releasing t h e 1
G A , Hulett and H. D . Minchin, P h y s . Rei-., 2 1 (1905), 391.
pressure, thus venting t h e system. maining in t h e tubing immediately t h e supply bottle. T h e apparatus a n d does away with pouring from bothersome syphoning.
603
T h e solution redrains back into works admirably heavy bottles or
AGRICULTURAL EXPERIMENT STATIO\ AMHERST,~IASSACRUSETTS
AN IMPROVED BUNSEN DIFFUSION APPARATUS B y JEROME S MARCUS Recei\ed Februarq 27. 1917
I n a laboratory, where gas density is determined often a n d with only moderate accuracy, t h e Bunsen diffusion method has been found t h e quickest. There is no weighing, room temperature is used, a n d there are no liabilities of error from external conditions. The two chief factors of error are due t o t h e difficulty of collecting over mercury and transferring t o t h e apparatus t h e gas under investigation, and t h e irregularity of t h e action of t h e float. T h e apparatus shown in t h e sketch was designed t o eliminate both t h e float a n d t h e transference of mercury and gas, a t t h e same time securing a more uniform pressure on all determinations t h a n by the immersion method. S o t only is t h e manipulation reduced t o a minimum, b u t also the degree of accuracy increased. The glass tube A is fitted a t the t o p with a 3-way cock, opening t o t h e orifice D a n d t h e tube E . At t h e bottom i t is connected by t h e 3-way cock I , t o t h e mercury reservoir B and t h e t u b e F. T h e removable reservoir C may be a n y small vessel. For greater convenience t h e whole may be mounted on a board. T o standardize against air, cock 2 is opened to communicate w i t h E , while t h e mercury is run out of A through F by cock I . With 2 still open, I is turned t o allow mercury t o flow from B t o A till t h e meniscus reaches t h e mark z . Both cocks are then closed, and B is filled from C t o t h e mark s. At t h e same time both cocks are turned, so t h a t A opens t o D a t t h e t o p a n d B a t the bottom. By means of a stop-watch, t h e time for t h e meniscus t o move from t h e y t o t h e x is determined. T o determine t h e rate of diffusion of t h e gas for t h e comparison t o t h a t of air, 2 is opened t o E , and A filled with mercury from B through I . Cock 2 is then closed. The reservoir C is moved up t o close t h e bottom of F , which is then connected t o A b y I . This makes A t h e mercury-filled vessel in which t h e gas is collected. E is connected t o t h e source of dry gas, a n d then connected t o A b y a . T h e gas entering A drives out t h e mercury into C, against t h e difference in pressure between t h a t of t h e atmosphere a n d of t h e mercury column in A . The mercury levels are brought t o t h e marks r and s as before a n d t h e r a t e of diffusion measured. ~ ' J I \ E R S I T S OF C O L O R 4 D O
BOLLDER
