Pagina-afbeeldingen
PDF
ePub

Methods 2 and 3 yield very fine lake pigments, but they are more costly to make than those made by the general method.

4th Method.—100 lbs. of alumina sulphate are mixed with a solution of 25 lbs. of Ponceau RR, and the whole heated to about 60° C., when a solution of 100 lbs. of barium chloride is added; the whole is boiled and then allowed to cool down a little, when a solution of 60 lbs. of soda crystals is added. Care must be taken in making this addition, as excess of alkali will adversely affect the shade of the resulting pigment. The barium chloride and alumina sulphate react with one another, forming barium sulphate, which acts as the base of the pigment, and aluminium chloride, which remains in solution this is precipitated on addition of the alkali in the form of alumina hydroxide, which combines with the dyestuff, thus forming the lake.

This method may be used with all colouring matters precipitated by alumina sulphate, and sometimes with others which are not so precipitated.

This process is not quite so good in its results as the second or third methods described above.

From paranitraniline may be prepared very fine scarlet red pigment lakes which work well with both oil and water, and keep their colour very well on exposure to light and air. The operations required must be carefully and accurately carried out in order to ensure success. The following method will give the best results :--14 lbs. of paranitraniline are mixed with 30 lbs. of good hydrochloric acid (it is best to use the pure acid, as the impurities in the commercial grades are liable to affect the brightness of the lake) and 25 gallons of boiling water. This, mixture is well stirred until all the paranitraniline is dissolved, allowed to cool, 25 gallons of cold water are added, and then, slowly and with constant stirring, 10 lbs. nitrite of soda dissolved in 10 gallons of water. This stage being the most important, special care should be taken to make the solutions quite cold and to mix the ingredients slowly. After about onehalf to three-quarters of an hour the preparation will be ready for the next stage. To the mixture is added 150 lbs. of barytes or other white base, and 30 lbs. of acetate of soda in 25 gallons of water. Next, 14 lbs. of beta-naphthol are dissolved with a little heat in 4 lbs. of caustic soda (77 per cent.) and 25 gallons of water; 25 gallons of cold water are then added, and, when the whole is cold, the beta-naphthol solution is added, slowly and with constant stirring, to the preparation of paranitraniline. The scarlet lake forms at once, and can be filtered, washed, and dried in the usual way; but in drying the temperature must be kept low.

This lake is prepared in fair quantities and sold under such names as Signal Red, Imperial Red, &c.

From alpha-naphthylamine may be prepared in a similar manner a fine crimson red lake. 14 lbs. of alpha-naphthylamine are gently heated with 30 lbs. of hydrochloric acid and 20 gallons of water until completely dissolved. The solution is then slowly poured into 30 gallons of water. The beta-naphthylamine will be precipitated as hydrochloride in the form of a fine white or faintly coloured precipitate. This is of no moment provided it be fine and not lumpy in character. The mixture must be allowed to become quite coid before passing on to the next stage. A solution of 10 lbs. of sodium nitrite in 10 gallons of cold water is made, and then poured into the alpha-naphthylamine mixture, the whole being kept constantly stirred for from one-half to three-quarters of an hour, when the operation will be ended. There is next added 30 lbs. of sodium acetate dissolved in 25 gallons of water, and 150 lbs. of barytes. To this mass is added slowly a solution of 14 lbs. beta-naphthol in 4 lbs. of caustic soda and 30 gallons of water.

The lake forms at once, and is washed, filtered, and dried in the usual manner.

ORANGE LAKES.-Any of the azo- or acid oranges may be used to make lakes by any of the methods described under the reds. The following are three recipes for making orange lakes :

1. 100 lbs. of base, 5 lbs. of orange G, 5 lbs. of barium chloride.

2. 100 lbs. of base, 3 lbs. of croceine orange, 4 lbs. of barium chloride, used according to the first method.

3. 62 lbs. of Glauber's salt, 10 lbs. of orange G, 70 lbs. of barium chloride, used according to method 3.

YELLOW LAKES.—The following recipes show the method of making yellow lakes from some of the azo-and acid yellows:

1. 100 lbs. of base, 3 lbs. of yellow N, 10 lbs. of lead acetate.

2. 100 lbs. of base, 3 lbs. of Indian yellow, 5 lbs. of barium chloride, used according to method 1.

3. 62 lbs, of Glauber's salt, 10 lbs. of Indian yellow, and 70 lbs. of barium chloride, used according to method 3.

BLUE LAKES.-1. 100 lbs. of base, 2 lbs. of Victoria blue R, 5 lbs. of barium chloride.

2. 100 lbs. of base, 2 lbs. of alkaline blue, 5 lbs. of barium chloride.

3. 100 lbs. of base, 3 lbs. of alkaline blue, 4 lbs. of lead acetate.

There are many shades of alkaline blue, ranging from a very red shade 4R, to a very blue shade 6B, so that a great variety of tints or shades of lakes can be made; the proportions of colouring matter and precipitant given are only approximate.

and necessarily they will vary with the kind and make of alkaline blue used.

These recipes are used according to method 1, given under the red lakes.

4. 62 lbs. of Glauber's salt, 2 lbs. of alkaline blue, 70 lbs. of barium chloride, used according to method 3, described under red lakes.

BROWN LAKES.—1. 100 lbs. of base, 3 lbs. of orchil brown B, 6 lbs. of barium chloride.

2. 100 lbs. of base, 10 lbs. of cotton brown A, 20 lbs. of barium chloride. Both used according to method 1.

3. 62 lbs. of Glauber's salt, 10 lbs of cotton brown A, 85 lbs. of barium chloride, used accordin to method 3. This gives a dark reddish shade of brown lake.

VIOLET LAKES.—1. 100 lbs. of base, 3 lbs. of acid mauve B, 15 lbs. of barium chloride. This gives a red shade of violet lake.

2. 100 lbs. of base, 3 lbs. of acid violet 6B, 10 lbs. of barium chloride. This gives a blue shade of violet lake.

Like the alkaline blues and the basic violets, the acid violets are made in a variety of shades, from a red 3R to a blue 6B, so that quite a large range of violet lakes, from a red to a violet hue, can be made from the acid violets.

Both these recipes are to be used as described under method 1 of red lakes.

3. 62 lbs. of Glauber's salt, 2 lbs. of acid violet 3B, 72 lbs. of barium chloride, used according to the third method.

BLACK LAKE.—100 lbs. of base, 10 lbs. of naphthol black B, 15 lbs. of barium chloride. This gives a rather grey shade of black.

GREEN LAKE.-100 lbs. of base, 5 lbs. of naphthol green B, 40 lbs, of lead acetate; the addition of a little ammonia completes the precipitation; the lake obtained is of an olive-green shade.

It is obvious that, in all the above recipes for making lakes from the acid coal-tar colours, by varying the proportions between the base and the colouring matter, a great variety of tints can be obtained from the same dyestuff; still, it is advisable not to reduce the proportion of dyestuff too much or the resulting lake will have too chalky an appearance. In this connection it may be mentioned that barytes makes the best pale-tinted lakes; china clay cannot be used very satisfactorily for this purpose, as, unless a large proportion of dyestuff is used along with it, it is apt to make chalky-looking lake-pigments. Necessarily, if the proportion of dyestuff to base be reduced, the quantity of precipitant required will also be less; the quantities of these

given in all the above recipes should only be taken as approximate; each particular sample of dyestuff will take its own proportion of precipitant, and as the actual quality of a dyestuff varies with different makers, it is scarcely possible to give very exact proportions, unless, of course, the maker's name were inserted, and this it is not deemed desirable to do in this book.

LAKES FROM ADJECTIVE COAL-TAR COLOURING

MATTERS. The third group of coal-tar colours are called the adjective or sometimes the mordant dyeing, dyestuffs, from the fact that, as already pointed out, they require the aid of a mordant, as it is called, to properly develop and fix the colour; in the most representative members of this group, alizarine, nitrosoresorcin, gambine, &c., the colour which is formed varies with the mordant used (see p. 260). Most, if not all, the dyestuffs which belong to this group possess acid properties, and have the property of combining with metallic oxides, like those of alumina, iron, chrome, tin, lead, &c., to form compounds which are more or less coloured, and quite insoluble in water; it is on this property that their value in dyeing, calico-printing, or in lake-making depends. In the two former arts the colour lake resulting from the combination of the dyestuff with the metallic oxide is formed on the fibre, while in the last it is formed in the free condition or on a base of some kind. The general principle which underlies the various processes for the preparation of lake pigments from this group of dyestuffs is that of bringing the dyestuff into contact with the oxide of the metal with which it is desired to combine it, and thus cause the colour lake to be formed.

The principal colouring matters of this group are alizarine and purpurine; these two bodies are sold under the general name of alizarine, which is made in several brands distinguished by letters, AB, SX, V, G, &c. Practically, there are two kinds of alizarine-alizarine yellow shade, which, with alumina, gives scarlet reds, and consists principally of alizarine; the other kind is the alizarine blue shade, which, with alumina, gives more crimson reds than the last, and consists mostly of purpurine. Then there are alizarine blue, alizarine yellow, alizarine cyanine, gallein, gallocyanine, galloflavine, nitrosoresorcin, gambine, &c.

ALIZÅRINE LAKES.– Various processes can be employed for converting alizarine into lakes. 1. Pure Alizarine Lake.-Mix 20 ozs. of ordinary commercial

alizarine* with ly galls. of water; then add 10 ozs. of alumina sulphate previously dissolved in water, and 2 ozs. of calcium acetate dissolved in water; boil the whole together for about an hour; then add 10 ozs. of soda crystals dissolved in water in small quantities at a time, at intervals long enough to allow of the subsidence of the effervescence thus set up. The whole mass is now boiled for about an hour, then allowed to stand for 24 hours, filtered, washed, and dried. This makes a dark red lake of good body and staining power. The shade or tint will depend upon the kind of alizarine used. Excess of soda crystals should be avoided, as it causes the lake to be of a dark colour.

2. Dark Red Alizarine Lake Diffuse 100 lbs. of barytes through 50 gallons of water, add 20 lbs. of alizarine, 10 lbs. of alumina sulphate, and 2 parts calcium acetate; stir well together, and then allow to stand for two or three hours, stirring at intervals to keep the ingredients well mixed. Heat slowly, so as to take about two hours to reach the boiling point, and, at intervals, add portions of a solution of 10 lbs. of soda crystals. Much of the beauty of the resulting lake depends on the care exercised during this stage of the process; too rapid heating, and too rapid addition of the soda crystals, has a tendency to cause the shade of the lake to be darker than it should be. The lake obtained by this process is of a fine ruby red colour. After it is formed, as described above, it is finished in the usual way.

3. Alizarine Lake.—Diffuse 100 lbs. of barytes through 50 gallons of water, add 10 lbs. of oleine or Turkey-red oil, and boil for one hour; allow to stand for twenty-four hours, stirring up at intervals, add 20 lbs. of alumina acetate (12° Tw.), and 2 lbs. of calcium acetate, stir all well together, and allow to stand for two days; then boil well for two hours, adding at the same time 5 lbs. of soda crystals. When the lake has formed, filter off, wash, and dry.

4. Alizarine Red Lake.—6 lbs. of alumina sulphate are dis-solved in water, and to this solution one of 1 lb. of calcium chloride is added; a precipitate of calcium sulphate is obtained, but, before this has had time to settle out, a solution of 44 lbs. of soda crystals is added; the precipitate of alumina and calcium sulphate thus obtained is collected on a filter and washed. It is

* Nearly all the so-called alizarine colours are sold in the form of a paste, containing about 20 per cent. of actual colouring matter. The reason for this form is that, as a rule, these dyestuffs are insoluble in water, and it has been found by practical experience that if sold in a dry form that the dyestuff does not mix well with water, and that they thus give rise to uneven dyeing, while the paste form mixes very well with water, and uneven dyeing rarely occurs.

« VorigeDoorgaan »