Tannin lakes

In the commoner cases the base is a hydrated metallic oxide (of aluminium, tin, lead, zinc or, less often, chromium, iron, copper, antimony) to which the colouring matter (if acid) is united by true chemical combination tannin lakes are also made (with basic colouring matters). In other lakes the base is an inert substance (barium sulphate, precipitated alumina and silica, chalk, gypsum, kaolin, etc.), on which the colouring matter is fixed by simple mechanical absorption. Lakes of the former kind may be mixed, either fraudulently or for the purpose of attenuating the colour, with inert materials. 

The tannates of all colour-bases are insoluble in water, but mostly dissolve in dilute acetic acid. The dyestuff is printed along with tannin and dilute acetic acid. The acetic-acid solution of the tannin lake penetrates the fibre, and subsequent steaming removes acetic acid, leaving an insoluble lake on the fibre. The shades may be made faster to soap by passing through tartar emetic. 

H NMR data from these seven sites are presented by spectral peak-height ratios in Table III. The sites were listed in order of increasing aromatic plus olefinic carbon percentages. Fulvic acids from all the lake samples are much lower in aromatic plus oleflnic carbon content than those from river samples. These results confirm the hypothesis that autothonous inputs result in dissolved humic substances that have a low aromatic plus oleflnic carbon content. The lake samples also are lower in the ratios of peak 2 (carboxylated chains and aliphatic ketones), peak 3 (carbohydrates), and peak 4 (phenolic tannins and lignins) to peak 1 (branched methyl groups and alicyclic ali-phatics) than are the river samples. 

Reasons for proliferation of poisonons weeds in livestock pastures Effect of tannin and tea gronnds on feeding by gray squirrels Gnstatory responses of lake stnrgeon (Acipenserfulvescens) imeaiXt , to extracts of natnral prey and amino acids... 

Lake A type of organic pigment prepared from water-soluble acid dyes, precipitated on an inert substrate by means of a metallic salt, tannin, or other reagents. Lakes were used in plastics at one time, but have been replaced by more permanent pigments. 

Continental Waters. Some data have recently been obtained for Central Kazakstan (Table 25) on waters in cracks and sediments of Devonian volcanics and sediments and water from the Sea of Azov and Lake Balkash (Andreyev et al, 1967). In this difficult analitical problem, the lead was collected either (1) on activated charcoal saturated with chloroform saturated with dithizone or (2) as a coprecipitate with a tannin-gelatin complex. The transient water was found to be highly variable in lead isotope ratios, both radiogenic and non-radiogenic and the lake waters had about the same ratios as oceanic manganese nodules or were less radiogenic. 

Evidence of this technique has been found by the present authors in a sample of a pink pigment containing textile fibres and tannins excavated from Pompeii, dating to the second century ad (Walsh et al., 2004) and fibres have also been found within a sample of red lake from Titian s Venus and Adonis (c. 1560) analysed at the J. Paul Getty Museum (Birkmaier et al., 1995). 

Some researchers have also questioned whether the trend toward acidified lakes is the result of acid deposition or other causes. For example, naturally acidic lakes can be found in the eastern U.S. These are generally clear lakes with a telltale brown color. (The color is due to organic acids, such as the tannins which give tea its distinctive hue.) They include peatland lakes in the Northeast and cypress swamps in the South. However, naturally acidic lakes are distinct from the so-called "oligo-trophic" lakes which are the focus of concern in the U.S., Canada, and Scandinavia. ... 

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