The Chemical Gazette 325, 1.5.1856
By Paul Schützenberger.
The author has instituted various experiments with madder, with the view of coming to some conclusion as to the pectine bodies contained in it. Madder from Avignon was extracted with four times its weight of water by maceration for ten minutes at 59°F. The extract furnished a moderate flocculent precipitate with alcohol, and on standing deposited a gelatinous mass, although in no great abundance; this had taken up the colouring matter. The precipitate produced by alcohol is, according to the author, pectate of potash, and the extract of madder contains no pectine. Under the name of “pectic acid” the author includes pectosic acid, pectic acid, and parapectic acid (which however is soluble in water); and under the name of “pectine,” the pectine, parapectine, and metapectine of Fremy, as he leaves it undecided which of these particular matters is present in each case. This appears from the fact that the extract gives a flocculent precipitate with muriatic acid, and the fluid filtered from this is no longer precipitated by alcohol. The gelatinous mass formed when the extract is left to stand is pectic acid, the separation of which is probably induced by another organic acid which is formed in the extract. Alsatian madder, treated in the same way, gave the same results, but it contained much more pectic acid than the Avignon madder.
When madder is boiled for a few minutes with water containing muriatic acid, the extract mixed with alcohol, the precipitate thus produced dissolved in hot water, and this process repeated until the separation of the colouring matter, a colourless gelatinous body is obtained, which behaves like pectine. As however no pectine was found in the madder itself, the author concludes that the latter contains pectose, and that pectine is formed from this body by the action of the muriatic acid. Pectose was thus found in Alsatian and Avignon madder, and in madder flowers, but not in garancine. The author has determined the amount of pectose in the madder from the weight of the pectine, dried at 212°F., obtained by boiling madder for five minutes with water containing muriatic acid (50 cub. centims. muriatic acid to 1 litre of water), which he supposes to have the same composition as pectose; in this way he has found in Avignon madder 23, in Alsatian madder 2:13, and in madder flowers 1 to 1:05 per cent of pectose. The smaller quantity of pectose in the madder flowers is accounted for by the fact that in their preparation a portion of the pectose is converted into pectine by the action of the acidulated water, and is removed in this form by washing.
The author also tried whether the madder contained any pectic acid besides the small quantity which is present in combination with potash. For this purpose he treated the madder extracted by acidulated water with solution of soda of 5°. The alkaline extract gave an abundant, flocculent, gelatinous precipitate with muriatic acid; this took up all the colouring matter. When the muriatic acid was allowed to mix very slowly with the fluid by pouring it carefully upon the bottom of the vessel, the whole fluid set into a gelatinous mass, in consequence of the gradual separation of the pectic acid; this is just like the jelly formed in the water in which certain samples of madder have been macerated. The pectic acid precipitated by muriatic acid was freed from the colouring matter by extraction with wood-spirit; but it was then coloured brownish by a humus-like body. To get rid of this, the pectic acid was dissolved in weak ammonia at a gentle heat, the solution was filtered, and the pectic acid then thrown down again by muriatic acid, when it was tolerably pure. Madder, therefore, as well as madder flowers, contains, be. sides pectose, pectic acid, which is contained in it in small proportion as pectosic acid.
If powdered madder be treated with solution of soda of 5° at 194°F., and washed until the water runs away colourless and no longer contains pectic acid, the residue is still of a strong violet-red colour. If this residue be treated with water containing muriatic acid, assisted by heat, and then again with solution of soda, the latter again extracts a large quantity of colouring matter and pectic acid, by which means the residue is entirely freed from colouring matter, and acquires the appearance of sawdust. This result is explained by the author as owing to the presence of a certain quantity of pectate of lime in the madder. This, and not, as has been supposed, the woody fibre, retains a portion of the colouring matter, so that it is not extracted by alkali; and it is not until the pectate of lime is decomposed by muriatic acid, that the colouring matter can be completely extracted with the pectic acid.
The author endeavoured to determine the amount of pectic acid in madder. For this purpose the madder was treated first with solution of soda, then with water containing muriatic acid, and afterwards again with solution of soda. The pectic acid was precipitated from the two alkaline extracts by muriatic acid, purified by the above-described treatment with wood-spirit and ammonia, and then dried at 212°F. Avignon madder, dried at 212°, treated in this manner, furnished, on the average of six very concordant experiments, 9.5 per cent. of pectic acid. If we deduct from this the 23 per cent. of pectose found in this description of madder, which is also converted into pectic acid by this process, it appears that Avignon madder contains 7.2 per cent of pectic acid, of which according to the author, about 2 per cent, are combined with lime. In the same way the author found that after the deduction of the pectose, Alsatian madder contained 6.4 per cent. of pectic acid, of which about 1 per cent, is combined with lime. In madder flowers he found on the average 10.5 per cent. of pectic acid. The amount of this acid combined with potash in the madder, which is the cause of the aqueous extract of madder becoming slimy or gelatinous by standing, is not more than 0.2 per cent. according to the author.
After the discovery of these large quantities of pectine bodies in madder, which have hitherto been regarded more or less as wood fibre, the author proceeded to determine the amount of the latter substance in madder. With this view he dried and weighed the residue of the treatment with solution of soda and muriatic acid just described, and deducted from the weight thus obtained, the amount of ashes left on the combustion of the residue; the remainder was considered to be pure woody fibre. In this way he found that Avignon madder, dried at 212°F, contained 19 to 19.5 per cent. of woody fibre, whereas, according to previous analyses, in which it is probable pectose and pectic acid were taken for woody fibre, the amount of this body was supposed to be 33 to 35 per cent. Alsatian madder contained 23, and madder flowers 30 per cent. of woody fibre.
In garancine, dried at 212°F., subjected to the same treatment, the author found 16.5 per cent of pectic acid (for the most part free, but partly combined with lime) and 48 per cent of woody fibre, which was less changed than is generally supposed. If we suppose that madder furnishes 40 per cent of its weight of garan cine, and that it contains 20 per cent. of woody fibre, the amount of the latter contained in the garancine should be 50 per cent. The number 48 obtained consequently indicates that the woody fibre undergoes no considerable loss of weight in the preparation of garancine. A similar calculation, supposing the garancine to be prepared from Avignon madder, which appears to be the case, shows that it should contain 18 per cent. of pectic acid, if no portion of this be destroyed in the preparation of garancine. The product occurring in commerce under the name of alizarine also contains pectic acid partly free and partly combined with lime, but its amount does not exceed 5 per cent. The woody fibre obtained from this was black, and had undergone a far greater change than that of garancine.
When 10 grms. of Avignon madder were boiled with water, 18 cub. centims. of carbonic acid were expelled; and by subsequently heating it with diluted muriatic acid, 66 cub. centims. were driven off. According to the author, this carbonic acid is combined with lime in the madder; and he supposes that the carbonic acid expelled by boiling with water is contained in it in the form of bicarbonate. The 66 cub. centims. of carbonic acid represent 0.27 grm., or 2.7 per cent. of the weight of madder, of carbonate of lime. In the ashes of the same madder the author found 5.7 per cent of carbonate of lime, from which it is to be supposed that a quantity of lime corresponding with 3 per cent. of carbonate is combined with organic acids, and especially with pectic acid. The whole of the lime in garancine and madder-lake, and nearly the whole in commercial alizarine, which is ſound in their ashes, is also combined with organic acids. It is remarkable that both garancine and madder-lake, although prepared by the treatment of madder with concentrated sulphuric acid, still contain pectic acid and pectate of lime.
According to the author, the woody fibre and free pectic acid cannot hold back the colouring matter of the madder. Pectate of lime however appears to do this energetically. If pectate of lime be artificially produced by double decomposition, by means of an alkaline solution containing colouring matter, the latter passes into the gelatinous precipitate, and cannot be extracted therefrom either by alkali or wood-spirit. The solubility of the colouring matter of madder in cold water, according to the author, is to be ascribed to the presence of pectate of potash. According to the author, madder also contains the nitrogenous ferment to which Fremy has given the name of pectose, both in the soluble and in the insoluble state; in the latter however in the largest amount. The analyses of ashes given by the author are as follows. All the substances were dried at 212°F.: —
10 grms. of Avignon madder gave 1.363 grm. of ashes, of which
0.300 grm. was soluble in water, consisting of chloride of potassium and a very little carbonate of potash, and
1.063 grm. insoluble in water, in which were found
0.29 grm. silica,
0.572 grm. carbonate of lime,
0.193 grm. phosphate of lime (precipitated by ammonia from the solution in muriatic acid).
10 grms, of madder flowers gave 1.263 grm. of ashes, of which
0.077 grm. was soluble in water. This portion consisted of
0.068 grm. sulphate of lime, and
0.009 grm. chloride of potassium;
1.185 grm. insoluble in water, containing
0.328 grm. silica,
0.624 grm. carbonate of lime,
0.170 grm. phosphate of lime.
10 grms. of garancine gave 1775 grm. of ashes, of which
0.106 grm. was soluble, and consisted of CaO, SO3, and
1.669 grm, insoluble, containing
1.02 grm. silica,
0.448 grm. carbonate of lime, and
0.19 grm. phosphate of lime.
10 grms. of commercial alizarine gave 1.18 grm, of ashes, of which
0.003 grm. was soluble, and
1.177 grm. insoluble. The latter contained
0.814 grm. silica,
0.256 grm. carbonate of lime, and
1.103 grm. phosphate of lime.
10 grms. of madder-lake gave 1.20 grm, of ashes, of which
0.195 grm. was soluble, consisting of CaO, SO3. The insoluble portion contained
0.450 grm. silica, and
0.550 grm. carbonate of lime with traces of phosphate.
- Polytechn. Centralblatt, 1856, p. 292.
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