- Title
- A study on white leather tannage
- Creator
- Williams-Wynn, D A
- Subject
- Uncatalogued
- Date
- 1950
- Type
- Diploma theses
- Type
- text
- Identifier
- http://hdl.handle.net/10962/193713
- Identifier
- vital:45389
- Description
- As has been noted in the previous section little or no complex formation occurs with either formate or acetate except possibly above pH 9*0 or so. These anions do not stabilise the aluminium solutions to precipitation - they may* however, be of value in controlling pH, as solutions of these salts buffer strongly in the region pH 4 to 5. The other salts, lactate, tartrate and citrate all show tendencies to complex formation though the degree to which this occurs varies with the anion. The complexes formed by lactate at high pH must be very unstable because on the addition of acid the pH corresponds to the calculated blank. Below pH 9.0 however, the curves deviate quite considerably showing that more acid must be added to reach a certain pH value than is required by the blank. This means complex formation has occurred with loss of -COGH groups. In this system too, buffering is apparent. The same is true of tartrate but this salt is not as efficient a buffering agent. This is probably due to the fact that the excess tartrate is not available as a buffer as it is precipitated as the acid salt which is only sparingly soluble. Citrate on the other hand must form very stable complexes, the effect of which is apparent at even very high pH values. In other words, addition of strong acid liberates free -GOGH groups which are immediately incorporated in the complex. This evidently does not occur with lactate or tartrate until lower pH values are reached. The ratio of lactate and citrate to aluminium appears to have some influence on the degree of masking as greater complex formation is found to occur at the higher ratio levels. Tartrate on the other hand apparently has a fixed complex forming capacity between 1 and 4 mols/mol aluminium, since the same deviation from the blank was observed irrespective of which ratio of the masking agent to aluminium, was employed. However, at ratios of less than 1 mol tartrate/mol aluminium, deviations from the blank were reduced and less stabilisation occurs as evidenced by the formation of precipitates containing aluminium under these conditions. In view of these facts it may be suggested that 1 mol tartrate combines with 1 mol aluminium to form a complex containing equimolar proportions of aluminium and tartrate. The effect of boiling apart from one or two exceptions always has the same effect, i.e. a shift to the acid side of the curve. Free acid must have been liberated which is an indication that olation might have occurred. In the lactate and citrate series dilution appears to reduce the complex forming capacity of these ions but tartrate is unaffected. Thus it would appear that the tartrate complex is more stable than those formed by lactate. Citrate stabilises aluminium solutions with fewer equivalents than tartrate, but the complex does not contain a constant ratio of masking agent to aluminium further quantities of tartrate cannot enter the complex even in the presence of large excess of the anion probably due to the effect of steric hindrance.
- Description
- Thesis (Dip) -- Leather Industries Research Institute, 1950
- Format
- computer, online resource, application/pdf, 1 online resource (120 pages), pdf
- Publisher
- Leather Industries Research Institute
- Language
- English
- Rights
- Williams-Wynn, D A
- Rights
- Attribution 4.0 International (CC BY 4.0)
- Rights
- Open Access
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | WILLIAMS-WYNN-T282.pdf | 7 MB | Adobe Acrobat PDF | View Details Download |