sion of acid coal-tar colours into pigments are based, and enable any intelligent colour-maker to apply them in producing a lake from any colouring matter belonging to this group.

Among the lakes of this group are the vermilionettes and royal reds.

VERMILIONETTES AND ROYAL REDS.-Vermilionettes were introduced to this country some twelve or fourteen years ago by the Silicate Paint Company of Liverpool, as a substitute for vermilion, which they have displaced to a considerable extent. Royal reds were introduced by Messrs. J. B. Freeman & Company of London. These pigments, and some others, sold under a variety of fancy names (such as Victoria reds, signal-reds, &c.) owe their brilliant colour to eosine; the deeper shades of the vermilionettes and the royal reds also contain orange lead; this is used for two reasons, one is to make the pigment heavy, and a closer imitation of vermilion, the other is to increase the depth of colour and the body.

These two pigments are made in a great variety of tints, from a very pale pinkish-red to a very deep scarlet; most makers keep several shades of both in stock. Vermilionettes are now made from barytes and eosine, with a precipitating agent, although, when first introduced, they contained orange lead as well, and some makes do so now; royal reds contain both barytes and orange lead as well as the eosine. The precipitating agent most used is lead acetate, although alum is also used occasionally.

The tint and brilliancy of these pigments depend largely upon the kind of eosine used. There are several varieties of eosines made, of which the following are the principal. They are all very bright scarlet dyestuffs, and may be divided into blue-shade eosines and yellow-shade eosines, distinguished by the marks B or BN for the former, and by J or G for the latter; these being the most useful for vermilionette-making

6

Eosine A, Eosine J, Eosine GG, is usually the potassium salt of tetrabromfluorescein, C20 H Br4 05 K2, and of a yellow shade. Eosine BN, Safrosin, is the potassium salt of dibromodinitrofluorescein, C20 H6 Br2 N2 O, K2, and belongs to the blue-shade

eosines.

9

Erythrosine, Eosine J, is the potassium salt of tetraiodfluorescein, C20 He I4 O, K2; it gives very blue shades of ver

milionettes.

6

Phloxine, Erythrosine B, and Phloxine T are bromo-chloroderivatives of fluorescein, and yield blue shades of vermilionettes.

Rose Bengale is a very fine blue-shade eosine; chemically, it is the potassium salt of tetraiod - dichlor - fluorescein, C20 H6 Cl2 14 05 K2

To prepare vermilionettes or royal reds the method generally pursued is to diffuse the base, which may be either barytes or orange lead, or both, through water, to add the required quantity of eosine, and to heat the mass to about 160° F.; then there is slowly added, with constant stirring, a solution of lead acetate until all the eosine is precipitated out; lastly, the pigment is allowed to settle, and is finished in the usual way.

The following recipes for preparing several shades of these pigments exemplify the quantities of the materials used:

The tint, as already noticed, will depend upon the chemical composition of the eosine which is used, while the depth of colour of the red will depend largely upon the quality of the make of eosine as well as upon the quantity of dyestuff used. By regulating the proportion of base to dyestuff many shades of vermilionettes and royal reds may be obtained, but, inasmuch as the eosine prepared by one maker greatly differs in quality from that of another maker, although professedly of the same chemical composition, it follows that the same shade of pigment may not be obtained from two makers' eosines. The proportion of lead acetate which is required to completely precipitate the eosine will also vary with the make of eosine used; it ranges from 2 to 4 times the weight of the dyestuff; colour-makers should always ascertain by a preliminary trial the precise amount required for any particular sample of eosine. When the pigment is properly made all the eosine is precipitated, and the wash waters are quite, or almost, colourless.

Instead of lead acetate, alum or alumina sulphate may be used; but the author considers that these are weaker precipitants and that they yield a pigment of inferior hue and permanence. The following recipes will show how these two salts may be used :—

VERMILIONETTES.

Barytes,

Eosine,

100 lbs.
11⁄2 lb.

100 lbs.

Alumina sulphate, 3 lbs. Alum, 10 lbs. Alum, 20

A very fine pigment may be made as follows:-50 lbs. of barium chloride, 3 lbs. of eosine, and 50 lbs. of alumina sulphate are dissolved separately in water; the eosine solution is run into the precipitating vat, and then the other two solutions are run in simultaneously; the vermilionette precipitates almost immediately, and is finished in the usual way.

Properties of Vermilionettes and Royal Reds. As pigments they are very brilliant in hue and have a good depth of colour, whether used as oil-colours or as water-colours, as well as good body or covering power. For colouring spirit-varnishes they are not good, as the eosine they contain is somewhat soluble in the spirit, and, consequently, the pigment loses its brilliant colour. One fault which they may have is that of blooming, due to the solubility of the colouring matter in the vehicle; this generally happens when insufficient lead acetate has been used to precipitate the eosine; in such cases the pigment usually contains some traces of free eosine, which passes into the vehicle and causes blooming.

They do not resist lengthened exposure to light and air; hence for work which must have permanence they cannot be recommended; still they will, if well made, stand a good deal of exposure, more especially if protected by a coat of varnish.

Vermilionettes and royal reds may be recognised by their greater or less solubility in alcohol, and by the solution showing a fluorescence, the character and colour of which will depend upon the particular eosine used in their preparation. Heat destroys the colour; if eosine and barytes alone have been used in preparing the pigment then the colour will be completely destroyed; but if orange lead has also been used then the residue will have a red colour. Nitric acid destroys the colour of these pigments. When orange lead is absent, then the colour is destroyed completely and at once; but if it is present, then the colour becomes darker and only disappears on boiling, and lead may be recognised in the solution.

SCARLET LAKES.-The number of scarlet and red azocolouring matters is very great, and most, if not all, of them can be made to yield pigments. It is practically impossible to deal with all these, but the recipes which are given will serve to show the

lines on which to work to transform the azo- and acid reds into lake-pigments.

The azo-scarlets are sold under such names as scarlet G, scarlet R, scarlet 2 R, scarlet 3 R, scarlet 2 R J, Ponceau R, double brilliant scarlet G, crystal scarlet 6 R, &c.; some of these names are common to several makers, but it does not follow that the scarlet G of one maker is the same product as the scarlet G of another maker; hence it may happen that while the one dyestuff will be precipitated by alumina sulphate, the other may not be.

All the azo- and acid reds are not available for making lake pigments; some yield very good lakes, others very poor ones. A few preliminary trials will show colour makers which are and which are not useful for this purpose.

For transforming the azo-colours, whether reds or yellows or oranges or other colours, four methods may be used; one or more recipes illustrative of each method will be given, and from them the colour maker can readily see how to make other pigments than those here mentioned.

1st Method.--General method of making given on p. 279. Bluish Scarlet.-100 lbs. of base, 3 lbs. of scarlet 2 R J, and 10 lbs. of barium chloride.

Scarlet.-100 lbs. of base, 5 lbs. of scarlet G, 20 lbs. of lead

acetate.

Scarlet.-100 lbs. of base, 3 lbs. of croceine scarlet M, 10 lbs. of lead acetate. A little ammonia completes the precipitation. Deep Crimson.-100 lbs. of base, 20 lbs. of amaranth, 60 lbs. of barium chloride. A little addition of sodium carbonate completes the precipitation.

2nd Method.-Mix in the precipitating vat lb. of eosine A, 5 lbs. of croceine scarlet M, and 33 lbs. of sodium sulphate (Glauber's salt). In separate vats dissolve 25 lbs. of barium chloride and 16 lbs. of lead acetate; when ready, run the barium chloride solution into the colour mixture, and then run in the lead solution. A very bright scarlet lake is thus obtained. This process may be applied to the preparation of lakes from two dyestuffs which require different precipitants.

3rd Method.-Very fine pigments can be made by the following process, which consists in dissolving in the precipitating vat 62 lbs. of Glauber's salt and 10 lbs. of scarlet R; into this solution is run a solution of 70 lbs. of barium chloride; the lake precipitated is finished in the usual way. By substituting for the scarlet R any other dyestuff which is precipitated by barium chloride other colours of lake pigments can be made.

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.

A