schultz's reagent.. how does it actually work?

[Ocean Breeze]

I had a request re the schultz reagent.
How does it actually work?
What is the chemistry behind the Zn + I ( also has K I in it)
And whats the reaction when the reagent meets the starch.

Also is there an alternative test for cellulose identification?

[ellice]

Dear Rainbow-sky,
Found a bottle of the stuff with "CORROSIVE" all over it! I remember making it along time ago for cellulose testing, which we don't seem to do anymore. Also found a hand written recipe

20g ZnCl2
1g KI
0.5g Iodine
Add ZnCl2 to 8.5mL water and warm to dissolve. Cool. Prepare a mixture of KI and Iodine in 20mL water. Add to ZnCl2 soln dropwise until Iodine precipitates, and persists on shaking.

I tried it on some cheesecloth, and turns from orange/brown to blue/black. Iodine on cheesecloth has no effect.
Schultz on starch turns blue/black.
Sorry, but can't help with the chemistry of the reaction.
Regards, Ellice.

[Ocker]

G'Day Barb I made up Shultz solution about 5 or 6 years ago and remember it was very concentrated sodium hydroxide and so extremely dangerous I advised teacher the little darlings should not touch it, (Demo only ) and it was never asked for again!

[Ocean Breeze]

yep, its rough as guts , but good stuff. it does provide a good test for cellulose, but the teacher wants to know what is happening chemically, both in the making of the reagent and also when it reacts with the cellulose.

I can tseem to find anything ont he net either.

[Ocean Breeze]

Still no takers on the chemistry behind it?

[Mother]

I am very surprised your teacher doesn't know the chemistry behind the reagent. I'm sure she is trained in chemistry right??? At your rate of pay it really is not for you to know.
Cheers
Mother

[Voice]

Well Mother, I was going to suggest the same thing. We are all brilliant, we know that, but there are some things that teachers have to do for themselves. Surely!!!!!!!!!
Maree

[Ocean Breeze]

yep, s'pose so.


So what is it??

[RosalieM]

I've tried googling it (with a mutitude of search terms) to see what comes up and it's really hard to find info on! I'm surprised by that... Now I'm curious to know how it works!

[Judy R]

All I know is it is a stain for cellulose.

[helenasgems]

Dear Rain bow sky,
I asked one of the young bright new additions to science and he said the zinc chloride is possibly the catalyst and causes the reaction to occur. The iodine causes the colour to change. Hope this helps.

[lada]

I understand that cellulose has to break down to react with iodine to form the colour change.
Maybe the ZnCl2 speeds up the reaction.
Lets keep digging until we find the answer
Lada

[Jazz]

Both starch and cellulose are polymers of glucose. We use Iodine/Potassium iodide, test for starch. Amylose in starch is responsible for the formation of a deep blue
color in the presence of iodine. The iodine molecule slips inside of the amylose coil.
Cellulose has a long chain and it is insoluble. Concentrated Zinc chloride solution dissolves cellulose to glucose.
Instead of Shultz solution (corrosive) we can use Amylase enzyme.
• Add 1mL of cellulose 0.5% cellulose solution, and same amount of amylase enzyme. Put in the hot oven for about 10 minutes.
• Place 1 mL of 0.5 % starch solution and 0.5% cellulose solution to two separate test tubes. Add 10 drops of iodine solution to each test tube and not the color.
• Once incubation of 5 % starch solution and 0.5% cellulose solution is completed, transfer half of each test tube into a two separate test tubes. To the original test tubes, add few drops of iodine solution and note your observations.
• To the second set of test tubes, add few drops of Benedict’s solution. Heat the test tubes in boiling water for 2 minutes

[J]

Ok so I just made my Schultz solution. How do I check to see if it works? Would like to test before it goes out to the class.

Thanks
J