3. Sorted FAQs on Wine Investigations

A. Properties of wine
1. Substances responsible for colour of red wine?
2. Chemical differences between red and white wine?
3. Effect of acids on taste?
 
B. Ageing of wine
1. Best way to age wine artificially?
2. What is ageing and how to accelerate?
3. Oxidation: how does it occur?
4. Cause of oxidation on standing?
5. Effect of SO₂ on ageing
6. Connection between wine and vinegar?
7. Changes in ethanol and ethanoic acid content with time?
8. No change in ethanoic conc. in 6 months?
9. Which increases as wine ages - total, fixed, or volatile acidity?
10.Link between wine ageing, oxidation and acidity?
11.Browning reactions in wine?
 
C. Titration of ethanol with dichromate
1. Best method to react with dichromate?
2. Back titration with dichromate: method?
3. Back titration with dichromate: theory?
4. Standardisation of K-dichromate: indicator?
5. Back titration: need for distillation?
6. Dichromate titration: before or after distillation?
7. Dichromate titration of ethanol: acidification?
8. Distillation vs dichromate titration: design of experiment?
9. Dichromate titration: indicator colour change?
10.Dichromate titration: complex formed with iron(III)?
11.How to use diphenylamine-4-sulphonate indicator?
12.Use of N-phenylanthranilic acid indicator - reaction?
13.How much H₃PO₄ to use/? How to make up indicator?
14.Alternative indicators?
15.Ethanol in perfume: dichromate/iodine back titration suitable?
16.% Ethanol by back titration: end-point?
17.Indicator for standardisation of dichromate with iron(II)?
 
D.Titration with NaOH
1. Definition of volatile acid?
2. Best way to titrate with NaOH?
3. Why distilled and why NaOH added before distillling?
4. How to calculate total acidity from NaOH titre?
5. Total acidity content: which acids?
6. Why NaOH not a primary standard?
7. Calculation of moles of hydroxide required
8. Acidity by titration: which K_a values to use?
9. Relationship between ethanol content and acidity?
10.Titration: how to find tartaric acid conc?
13.How to find end-point?
14.Titration curve for tartaric acid
 
E. pH Titration
1.How to use pH titration?
2.Acidity by pH titration: finding end-point?
3.pH titration: fixed total acidity?
4.pH titration: equivalance point?
5. Titration curve for tartaric acid
 
F. Sulphur dioxide determination
1. SO₂ Estimation: starting volume of wine?
2. Standardisation of thiosulphate: concentration needed?
3. SO₂ content: help with ripper method calculations
4. How ageing affects SO₂ content
5. SO₂ content with H₂O₂: why titrate with NaOH?
6. SO₂ content: help with calculations
7. Calculations to find SO₂ content?
8. Estimating SO₂: Why acidified? Source of constant (1280)?
9. Reaction of SO₂and iodine?
10.Link between SO₂ and ethanol content?
11.SO₂ determination: method using iodine solution?
12.SO₂ determination: use of activated charcoal in red wine?l
13.Titration with iodine: reaction with SO₂?
14.Conversion of aldehyde + SO₂
15.Why EDTA added to titration with iodine?
16.SO₂ in wine: why add NaOH?
 
G. Chromatography of acids
1. Detection of ethanoic acid by TLC?
2. TLC of acids: solvent and indicator?
3. TLC: methods for developing spots other than UV?
4. TLC: Do R_f values depend on solvent?
5. TLC: which acids are volatile?
6. TLC: reasons for solvent mixture and indicator?
7. TLC: paper instead of silica plates?
8. TLC for non-volatile acids?
9. TLC solvent mixture - use of formic acid? Indicator conditions?
 
H. Tannin content
1. How does tannin affect iron absorption in the body?
2. Methods of finding tannin conc?
3. Tannin determination using permanganate?
 
I. Colorimetry
1. Use of colorimeter for ethanol content: colour change?
2. Colorimetry using silver nitrate and dichromate?
3. Colorimetry as an alternative to dichromate titration?
 
J. Use of activated charcoal
1. Will activated charcoal affect results?
2. Use of activated charcoal to decolourise?
3.Use of activated charcoal?
 
K. Miscellaneous
1. How to use uncalibrated density bottle?
2. Why density needed to determine % ethanol?
3. Why wine made alkaline before titration?
4. Ethanol content: amount in ml or %?
5. Ethanol content of perfume by iodine titration?
6. How to determine esters by back titration?
 
See also the tutorial on Investigating Wine

updated: 07 August 2008