-onie alcoholic solution of mcthylene blue, a few 

 dn>p- at a time, "ii tile -urfacc of \\ater in a wutch-^las-. 1> CS 

 mixture taki place -lowly or rapidly: (In this case \\ e liave an 

 additional factor inv- .lve<l. change- in surface ten-ion.) Try in 

 tlu- -ami- wa\ an a|Ui-ou- -olmion of niethvlene blue. Are ibe results 

 it ? \\ li\ : 



lla\r a Uaker full "f water wbieh i- kept undisturbed. 

 and oh-er\e from the side. I 'laee on the -urface -onie powdered 

 metluleiie blue: ob-ervc the solution and diffusion. Describe accu- 

 !y what you - 



i i i. a. I'lace a lilanient "f Spiro^yru in a dilute solution I I drop 

 tn a wateh-.yla-- of \\ateri of neutral red in pond water. Is the dye 

 taken up: hoe- it beeome more eoneentrated than in the external 

 -nluiioii;- U thi- eonirary t" phy-ieal law-? l ; .\ainine the cells 

 under the inien>-eope and determine the condition in which the dye is 

 held within the cell. Ik-scribe. 



b. Place in another dilute solution of neutral red some Spirojjyra 

 tilanuiits that have hreii killed: (a) by immersion for one minute 

 in chloroform-saturated water, ibi by immersion for one minute 

 in boiling \\ater. How do tlii' re-ult- coni])are \\ith tho-e on living 

 ci-11 \plain. 



ill. Kepeat t-xperinient lio with l-'.lodea leaves. How i- the 

 d\e accnmulatid in these cells? U this in opposition to ]>hysieal 

 law- More concentrated dve may be nece-sarv here. 1 low does 

 I'.iiamecium take U|> neutral red. Try a very dilute dye - >lntii>n. 



SEMIPERMEABLE MEMBRANES AND OSMOSIS. 



iij. \\hat i- a setni-pcrmcable membrane.' Such membrane- 



ma\ be made a- follows; iai Introduce by a tine mouthed pijiette 



< u>< i, lielo\\ ilu- -urface of -'' - K 4 Fe(CN i,, in a watch-.^la--. 



\\'hat i- the membrane formed? Give the reaction. ( >h-ervc the 



Doe- it change in thickness? Do the drops of 

 ( u>< i, ilnis formed change in size? If SO, why? 



1 b. i Tannate of gelatin membrane-: a -olnlion of _" , tannic acid 



tainin^' su^ar \ (> ,-<;. m _' conci-ntration i- allo\\ed to llow a- abo\i- 



i the ~urface.it" a noil -elatini/in^ m', i^.-latin -olntion. Study 



tin ( bara. ter "f the membrane, form, and changes of si/e as lu-fore. 



\\ hat part doe- the -n^'ar plav in this e\pi-rinient ? 



1l t!ii-,>n ; /li til>sr^ti<'ii ,'f zvatcr. Suspend by a thread 



m a 3^5 ( nS< i, -olution and place where 



be undi-turbed. Observe the general characteri-tic- and 



30 



