The iodide titration of silver nitrate with palladious nitrate as the indicator

Abstract

An ecological approach has been presented by valorisation of outer green shell of almond fruit as a novel natural dye using chemical solvent free extraction, small amount of metallic mordant, alternative natural mordants, auxiliary free dyeing and washing. The main objective of this study is to evaluate biomordants versus metal mordants and to reveal the substitution of the prevalent metallic mordants for biomordants as renewable natural sources. The use of a smaller amount of metallic mordant (0.2 g/L - 1 %) and less plant (1 g plant/3 g fabric) than in most current natural dye applications is a major advantage of dyeing with almond shell extract. Wool fabrics dyed using metallic mordants namely alum, iron II sulfate, copper II sulfate and potassium dichromate were compared with the samples dyed using biomordants; powder of valex (acorn of Quercus ithaburensis ssp. macrolepis), pomegranate (Punica granatum L.) rind, rosemary (Rosmarinus officinalis) and thuja (Thuja orientalis) leaves in terms of colour measurements, light and wash fastness values. These biomordants were used alone and in conjunction with almond shell extract in the same bath to dye wool fabric. Rose, brown, cinnamon and burgundy/reddish hues were achieved by using alum, iron II sulfate, copper II sulfate and potassium dichromate respectively. Especially rose and burgundy/reddish shades are unique colours for natural dyes. Biomordants exhibited different interactions with almond shell extract resulting in quite different colour gamuts. Rosemary can be alternative to alum (pre and post mordanting), iron II sulfate (pre mordanting) and copper II sulfate (pre, simultaneous and post mordanting). Thuja orientalis leaves, valex and pomegranate rind cannot be precisely substituted for any of the metallic mordants used in this research. However, thuja leaves with almond shell ensured relatively similar colours to alum (pre and post mordanting). Considering the fastness properties; thuja was not effective on washing and light fastness, valex and pomegranate rind improved both washing and light fastness, rosemary was not effective on light fastness while it slightly improved the washing fastness. Valex and pomegranate produced equal light fastness to copper and iron mordant while they exceeded that of the alum and chromium. The light fastness values of rosemary and thuja were similar to alum and chromium and less than copper and iron. Use of biomordants is very promising concept as an alternative method that may help to reduce the reliance on toxic metal salt mordants.