'20
A S E W F O R M O F 1)RUPI'ING
FLASK.
,4 N E W FORM O F DROPPING FLASK. I ~ YF. V. 1'001,. It is often convenient in methods of titratioii in the laboratory to make use of a flask or hottle from which the standard solution can be poured or droppwl arid t i i c airroiiiit of solution whic,h h:ts been used, dettsrmiiied b y weighing t h e fl:isk or bottle of liquid before aiid after t i l e opcrstion. This mcthod has severai advant a p s over tlie ordinary volumetric u n c i i i which aburc:te is used, the first advantage beiiig that of using the liquid at any ordinary temperature without m:tkiiig :1. correctioii for thc differelice between that temperature :ind the one a t wtricii the liqiiid was standardized, provided, of coui'se, that tlic staiidardizirig was made with tile flask and not witii ii biirette. This i.1 tliie t o the simplc fact that a gramme of water or any other liquid iceigks thc same, 1 1 0 matter whether thc t,ernperature be 15" C. or 20' C!., arid iF, i i i Ijrocesu of st:iridarclizing, for example, a solutioii of AgXO,, it is found that one gramme of the solution is equivaleiit to one milligramme (.oo I g r m . ) of GI, we m a y usc the solution (by wciglrt) afterwards a t the s:inie ternper:iture 01' ;my other temperature ortliiiarily foiind in t lie 1:~lorntoi.gwithout making any correction f o r the same. This i.: not the ca\c in using a n ur(1iiiai.y burette and rea(ling off the ciokmLe taken, t'or hcre we must nialte use of a table of correcti,ins for ternpwatuw, ~rliichwcinltl givc us f o r a range of 10' C.--.ay, between 25' C. ant1 1:)' C., a cIiffci~!n~e of . 2 of 1; of the atrc.ngth. Tliat i s t o say, i f i o 0 e.(*. of thi: sail1 solution are cqu;valerit to .loo grm. of Cl, a t 25' C. the same woluine of the liqiiid a t 15' C. woiiltl be eqnivnicrit to , 1002 C1. Of course this al'plies to ail biirettes whicli recortl thc voiiime of liquid taken. In the second place tlie dropping fla.;k 11:~s:iii advaiilage over burettes which require the use of a pinclicuclt and rubber tube, innsmuch as we may employ in the flask :i solution such as permangnnnte of potash o r chromic :loid trhici; n-onld act injuriously upon the riil)bei. tribe aiid I v x o r u e itself clecoinposed. -Yo obviate t h i s difficillty i n the use of burettes, recourse is had to glass stopcocks, whirl: art+expensive and not always perfect. They are also liable t o stick very tightly i f ztlioweci to remain for some time in coritact with 1< I10 ni* S a €10 solutim. T h e Gay Luss;rc: arid Bink burettes are not opeii to the second
A NEW FORM OF DROPPING FLASK.
21
objection, but they are attended with a di5culty which is peculiarly their own, namely, the retention of a drop of the solution at t h e end of the droppiiig tube by capillary attraction and the prevention of the free delivery of the contents of the burette. Analysts have overcome this difficulty I)y inserting a stopper, provided with a glass tube and rubber month tube, into the to]) of the burette and expelling the refractory drop wii h the breath. This procedure aiiswers very well, but there is a somewhat neater way as we shall see further on. T h e dropping flasks in use at the present nothing day are but few small i n , kittd flasks andofvery varying simple, capacity being
&
provided with a top or side tube and opeti to the objection which is found in using the burettes of Gay Lussac and Bink. The flask here shown is an improvement upon existing forms, and has been used for some time in the laboratory and with a great deal of satisfaction. It consists df a light, flat-hottomed flask of a size determined b y the capacity of the balance upon which i t is t o be weighed. From one side, near the bottom, a narrow titbe starts and reachefi 0 then turned up a little higher thaii the b0d.y of the flask, being outward like the side tube of Gay Lussac’s burette, which it resembles. I n the neck of t h e flask a s ~ d hole l is blowit which, during the operation of dropping, is governed by the thumb of the manipulator. Into the neck of the flask a rubber stopper is fitted and through this stopper B short thistle-tuhe is passed, t h e upper part of the latter being covered by a piece of thin sheet rubber, securely fastened by a piece of thread. T h e flask being filled with the standard solution is fiisst coiltiterpoised on the balance. It is then giasped aruund the neck, the thumb being placed very near the small hole in the side and the forefinger held j u h t over the rubber membrane on the top. The flask is then tipped so as to deliver the solution througb the side tube, the rapidity of flow being governed by the thumb, which closes the small hole in the neck a t will. If at any time during the operation a drop is formed a t the end of the tube, it can easily be forced out or drawn back into the flask hy thecontrol
o f the thumb and forefinger. Hy this means any amount of delivery may be obtained from pait of' a d r o p (by touching the end of the tulw t o tlw stirring rod) t o a steady stiwirn. M t e r a hufficierit quantity of the solution lias k e n used, its \\eight is detcLiniriedby rt placing the flask npon the balance pan and adding weights to balance the cuunterpoise i n tlie other pan. In our ow11 1;iboratory we use for this purpose a balance whose capacity is 300 grnninieu i i i each paii, and a eounteiyoise consisting of a small pasteboard box partly filled witli shot. FVith this it is tlie work of only a few seconds to cwunterbalaiice the flask, and after thc titration is completed, the. amount of solution used is quickly ascertained by the above metliod of leaving t,he couriterpoisc as it WBS and adding weights to t h e pan containing the flask. T h e capacity of the latter i 6 about 250 C.C. and one filliiig suffices for several operatibnr, the counterpoise being changed cnoh time b y rijnioving some of the shot. The convenience of this modified volumetric method can be apprecisted by those who usually have a nuniber of determinatioiis of oiie liiiid to make i n a J a y , and it, will recommend itself to all on account of the ease of manipulation, :icc.uracy, and slight cost of the apparatus. The adaptation of the above described contrivaiice to a Gay [,ussac burette, is obvious. All that is necessary is to adapt a rubber stopper and thistle-tube to the burette, and to blow or drill a s m d l hole into the side of the burette about an inch from the top. T h e flasks used werc made by William Baetz, 96 Fulton Street, New York.
XOTE ON OIL O F MALT.
BY NARCISSE PIGEON. (Abstract.) I h e r is properly inanufiictui~edfroM malt and hops, barley being the grain usually employed in making malt. None of the substitutes €or barley malt, contain the characteristic oil of malt and lack therefore the proper taste and aroma. Oil of malt has been fouiid by the author i n the radicles or rootlets of barley malt, and he suggests its extraction as a proper siibstirnce for developing the taate which is lacking in beer made from the abovementioned subst:mces.
