On The Coloring Matters Of Flowers
Chemists have only a very incomplete knowledge of dyes flowers.
Your investigation has problems that can not be wrong. The materials, flowers do not bloom; They are often altered by the action of reagents used in their preparation; And also very colorful flowers owe their color to very small amounts of dye.
On the type of dyes flowers, several opinions were expressed. Some observers have speculated that the flowers owe their color to two dyes, one of which is called an anthocyanin and the other anthoxanthine. Others will find a relationship between the green leaf color, chlorophyll and dyes flowers. They generally base their views on the results of the elementary analysis of these organizations; But all chemists know that chlorophyll is not produced in pure state. It probably holds different amounts of fat and protein bodies. In addition, dyes flowers are hardly known, so it is impossible to create long-term relationships with the necessarily uncertain composition of impure bodies.
Some time since the blue color of the flowers was attributed to the presence of indigo; But somehow the blue flower substance is still reddened by acids; And that with indigo, it is very different, as we know its blue color retains even when it is allowed to act on the strongest acids.
This shows that dyes flowers have so far only been addressed superficially, and it is important to begin their full testing because these are of interest to the chemist because they are used as reagents in the laboratory for lye recognition; And a better knowledge of them the florist might find the way with which he could give grown flowers of different colors.
Before their elemental analysis company, it should look carefully for methods that can be tracked to get dyes flowers and show whether these substances are independent site or when viewed from one of the same material that is produced in different ways by the juices of the plant will be changed.
Material blue flower coloring (cyanine).
The blue color of the flowers we recommend to call cyanine. For this material we need: Centauria cyanus, Viola odorata or Iris pseudacorus with boiling alcohol, through which flowers are discolored; And the liquid immediately gets a thin blue.
When we leave the coloring agent to spend some time in contact with alcohol, we see that the blue liquid disappears gradually, and soon a yellow-brown color takes its place. The coloring material in this case has suffered an actual reduction in prolonged alcohol action but will resume its original color when the alcohol is evaporated in the air. However, alcohol does not remain in contact with the coloring agent for too long because the alcoholic extract does not continue its blue color by the action of oxygen.
The remaining residue of the evaporation of the alcohol is treated with water which separates a fat and a resinous substance. The aqueous solution containing the coloring material is then precipitated by the neutral lead acetate. The precipitate, which has a fine green color, may be washed with water and then decomposed with hydrogen sulphide; The dye enters the aqueous solution, which is carefully evaporated in a water bath; The residue was dissolved in absolute alcohol; Finally, the alcoholic solution is mixed with ether, which precipitates the cyanine as blue herds.
Cyanine is not crystallizable, soluble in water and alcohol, insoluble in ether; Acids and acid salts the color red immediately; With alkalies, it is, as you know, green. Cyanine appears to behave as an acid, at least formed with lime, barium, strontium, lead oxide, etc., green-insoluble compounds in water.
The absorbent body oxygen, such as sulfuric acid, phosphorous acid, and the alcohols that fade; Under the influence of oxygen, its color is restored.
Rose red dye.
To extract the fabric pink-red color some dahlias, roses, pœonias used by alcohol. To this proxy colorant, the procedure followed exactly is the production of cyanine.
By carefully comparing the properties of this dye with those of the cyanine, we found that the rosarote dye is the same as blue, or at least the result of a modification of the same principle independent.
It appears in the pink-red modification, when the juice of the plant with which it comes into contact has an acid reaction.
This acid reaction in the juices of plants to red or pink color, while blue juice plants always showed an alkaline reaction.
Most red-pink or red flowers on the influence of alkalies and saw that they become blue for the first time and then green by their effect.
It is often found that some red-pink flowers like that of Mallow, especially those of Hibiscus syriacus acquire discoloration by a blue color and a green color, the change as we have seen is a decomposition of nitrogen-containing organic matter, Which are very often found in the petals. This body produces decomposition ammonia, which is associated with flowers blue or green. By the action of weak acids the petals can be restored to their pink-red color.
The discoloration of some pink-red flowers can also be observed when the leaves are dried very quickly, eg vacuum, which one can not easily assume that a body nitrogen decomposition of the evolution suffered from ammonia. Above all, we must say that the color changes in this case happens in purple, and never comes to green; And in addition, it is always accompanied by the development of carbonic acid, which one recognized by direct experience.
The petals that were previously red rose, and became violet light by drying, emitting carbonic acid; We can assume that the rosarote color is produced in the petals of this carbonic acid and that its expulsion The petals are blue color, characterized by the flowers neutral juice.
With certainty that the flowers of pink-red, violet or blue, owe their coloration to a single substance, but in various ways modified by the influence of plant juices.
The scarlet flowers also contain reddish cyanine by acid, but in this case the substance is mixed with a yellow dye, which we now describe.
Yellow Colour.
The simplest experiments show that an analogy exists between the substance, the colors of yellow flowers, and the ones we have already spoken.
The means that so easily occur with cyanine, the pink, purple or green coloring can in no case give these colors of the yellow substance that are obtained from flowers.
Through the different yellow flowers investigation we found that they owe their coloring to two substances which differ in their properties from one another and do not appear to derive from the same principle independently.
One is completely insoluble in water, which we gave Xanthin name Runge a yellow field madder. Since this name was not accepted in science, we have used to describe a coloring materials yellow flowers. The other substance is very soluble in water and is called xantheine.
Xanthine or yellow colorant is insoluble in water.
This dye is made from numerous yellow flowers, but above all Helianthus annuus.
To the flowers we deal with absolute boiling alcohol, which dissolves the dye in the heat dissipates, and still almost completely cooling to overthrow it. The yellow deposit is obtained, not a pure xanthine since it contains a considerable amount of oil. To separate this oil, we use a moderate saponification; Thus, the yellow precipitate was heated with a small amount of alkali to saponify the fatty substances to xanthine, which contains the same dissolved xanthine. Since the dye is soluble in the soaps solution, we do not treat the mass with water, but with acid-isolating xanthine and fatty acids is decomposed from the saponification. This precipitate treats us with cold alcohol, leaving behind fatty acids, and dissolves the xanthine. This substance is a fine yellow color, insoluble in water, but soluble in alcohol and ether, which are thus colored in yellow gold. It does not appear to crystallize and has the general properties of the resins.
Xanthine, in combination with the cyanine dye, as communicated by the various juices of plants, flowers in proportions of yellow-orange, scarlet red, and varies.
Xantheine or soluble coloring material in water.
For the manufacture of the fabric, some yellow dahlias, one immediately realizes that they have no analogy with xanthine.
The latter is known as water-insoluble, whereas the colorant is freely soluble in water.
For xanthine, we treat dahlias yellow flower with alcohol petals, which quickly dissolve the yellow dye, aside from fat and resin.
The solution is evaporated to dryness and the residue is treated with water so that the fat and the resin are separated. Water is again evaporated to dryness and the residue is treated with absolute alcohol. The resulting solution is diluted with water, mixed with neutral lead acetate, the dyes precipitate.
Lead precipitate is then decomposed with sulfuric acid, on which the xantheine, which remains dissolved in the water, is purified by alcohol.
Xantheine is soluble in water, alcohol and ether, but none of these solutions crystallize. Alkalies color it intensely brown. Its color strength is considerable.
He dyed various fabrics of a yellow clay, which is dull. Acid destroy again the brown coloring of bases. Xantheine combined with most metal bases and thus forms the yellow lakes or insoluble brown.
The facts told here are consistent with what was observed about dyes from flowers previously. It is known that blue flowers can become red, white and where their dye is destroyed, but never yellow - and vice versa.
These three dyes can produce color, either alone or by adding that we see in the flowers; But if they are the only materials that determine the flower color, we are currently unable to determine.
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