Bleachers' blue containing ferrocyanide of iron, used exclusively for bleaching purposes was held dutiable as an unenumerated manufactured article and not as a color under the act of 1897.-De Ronde v. United States, 1 Ct. Cust. Appls., 104, Abstract 26014, T. D. 31744, The blues referred to in paragraph 45 of the act of 1897 were declared to be blues in paints and colors.

BLACK PIGMENTS.

[Par. 53, act of 1913, 15 per cent ad valorem.]

SUMMARY.

Paragraph 53 of the tariff act of 1913 reads as follows:

Black pigments, made from bone, ivory, or vegetable substance, by whatever name known; gas black and lampblack, dry or ground in or mixed with oil or water, 15 per centum ad valorem.

This provision includes a wide variety of black materials, which when finely ground and mixed with the proper vehicle-e. g., linseed oil-will form paint. Carbon is the base for nearly all black pigments. Black pigments may be divided into five groups: (1) Soot blacks, which include lampblack, carbon black, gas black, acetylene black, benzol black, and other black pigments obtained by the incomplete combustion of many substances, such as natural gas, crude petroleum oil, dead oil (obtained from coal tar by distillation and from resinous woods, tar, and pitch). Carbon black, one of the most important of the class, is generally made by burning natural gas so that the flame impinges on a metal surface, where the carbon is deposited and later removed by scraping. It is largely used as a filler in rubber, in the manufacture of printing ink, in stove polishes, and in paints. (2) The animal blacks, which form the second group, are principally obtained by calcining bones. Certain high grades are made from ivory chips or from carefully selected bones. These are known as ivory black and drop black to distinguish them from the other forms of bone black. (3) The charcoal blacks are obtained by charring willow, maple, bass, and similar soft woods. A special grade product, known as vine black, is obtained by charring grape vines. (4) The mineral blacks are powdered shale or slate and appear in commerce under the names of mineral black, slate black, black chalk, etc. Powdered coal, graphite, manganese ores, and asphaltum are occasionally used as black pigments. (5) The fifth class are the black lakes, which consist of coloring matter precipitated onto an inert base such as barytes and aluminum hydroxide. Logwood, nigrosine, and other coal-tar dyes are largely used.

The manufacture of black pigments is a comparatively large industry, representing in 1914 an invested capital of $5,000,000, employing 437 persons, and having a total output valued at but slightly less than $3,000,000. This included 44,500,000 pounds of bone black valued at $1,532,000, 22,900,000 pounds of carbon black worth $918,000, and 11,200,000 pounds of lampblack with a reported value of $503,856. The output of carbon black in 1918 is estimated to have been practically double the 1914 production.

The United States has a considerable export trade in black pigments, especially in lampblack and carbon black. The value of the exports in 1914 amounted to about one-eighth of the total production.

Since that time there has been a large increase, due perhaps to the increased prices. In 1919 the exports reached a maximum of $1,573,740, which was practically double the highest figure reported before the war. England and other European countries have been our largest customers, though in recent years large quantities have been shipped to the Latin-American countries and to the Far East. Imports, on the other hand, have been very small and of little significance. The average value for the five years prior to the war (1910-1914) was $26,132. Since 1915, imports have been small and sporadic.

Black pigments were dutiable at 25 per cent ad valorem under the acts of 1883 and 1890. In 1894 the rate was reduced to 20 per cent, but in 1897 was returned to 25 per cent, which rate remained unchanged until reduced by the act of 1913 to 15 per cent.

The tariff classification of the two varieties of bone black have in the past occasioned considerable litigation. "Bone char not suitable for use as a pigment" which enters free of duty under paragraph 477. differs from pigment bone black only in that the latter is more finely ground.

! Includes animal charcoal and blacks used in fertilizers, sugar refining, etc., in addition to that used as pigment.

Fiscal years.

3 Calendar years.

4 Imports valued at $56 from Cuba (under reciprocity agreement).

GENERAL INFORMATION.

Tariff act of 1913.-Par. 53: "Black pigments, made from bone, ivory, or vegetable substance, by whatever name known; gas black and lampblack, dry or ground in or mixed with oil or water, 15 per centum ad valorem."

DESCRIPTION.

Black pigments almost invariably contain carbon as a base. There is a wide variety of these pigments and they are made from many different kinds of material and are known by many different names. But they can all be grouped under five groups, viz: (1) Soot black; (2) animal blacks; (3) charcoal blacks; (4) mineral blacks, and (5) black lakes.

(1) Soot blacks. Soot blacks are all obtained by the incomplete combustion of mineral oils, greases and fat-oils, resins, tarry matters, or natural gas. Acetylene black, which is obtained by the explosion of acetylene gas in a cylinder with a limited supply of air, may also fall in this group, as do lampblack, carbon black, gas black, smoke black, vegetable black, candle black, flame black, etc. The most important of these are described below.

Lampblack is the condensed smoke or soot produced by the partial combustion of organic substances. It is generally made from "dead oils" separated from coal tar or from the residues of petroleum refining. But where these products are not available, it may be made from resinous woods, tar, pitch, etc.

As now manufactured, lampblack is exceptionally pure, containing 99.5 per cent or more of carbon. Occasionally, however, samples are encountered that contain some unburned oil. According to Toch, this oil had to be removed by a naphtha treatment, but this is no longer necessary. The presence of oil prevents the drying of the paint within a reasonable length of time, as lampblack at best is a very slow drying paint material. It is one of the bulkiest of pigments. One pound of it, without undue pressure, will occupy over 200 cubic inches, often as much as 230 cubic inches (1 gallon). The color is distinctly gray as compared with the animal blacks or with carbon black. When tinted out with white, it has a bluish tinge, whereas bone blacks show brownish.

Carbon black 2 is similar to lampblack except that it has an intensely black color. While it has high tinctorial power, its use has been somewhat restricted in mixed paints because it produces a streaky color and separates out from the rest of the mixture. It is much used in printing ink, rubber compounding, for coloring cement mortar, etc. The product is free from oily matter and mixes well with water, but with difficulty with oil.

Carbon black is made by burning gas (especially natural gas) so that the flame impinges on a horizontal, rotating iron plate (frequently water-cooled). The sudden lowering of the temperature of the flame causes a deposit of carbon, which is removed from the plate by a scraper.

Benzol black is a carbon black made from benzol instead of gas.' (2) Animal blacks.-There are a great many animal blacks, varying from ivory black, which is obtained by the calcination of ivory chips, to sugar-house black, a by-product of the sugar mills. The composition of all these blacks is similar in that they all contain carbon and calcium phosphate. The carbon content varies from 10 to

1 Chemistry and Technology of Paints. Von Nestrand, 1916.

2 "Gas carbon" is the cake that gathers in the pipes and flues of by-product coke ovens, gas plants, and similar establishments. It is not a pigment, but is used principally for making artificial graphite. 3 Toch: Loc. cit.

4 Benzol is a product obtained in the distillation of coaltar.

20 per cent, the rest being phosphate of lime and moisture. A little carbonate of lime is sometimes present.

Some of the best blacks are made from the shin bone and skull of sheep, and these blacks have the most intense black color. The highest-priced blacks are those having the most intense black color and which will not settle out in varnish or oil. Such blacks are made by digesting carefully selected burnt bones or ivory chips in hydrochloric acid, which removes the lime salts and leaves the carbon in the form of a flocculent residue. This carbon is frequently sold under the name "black toner," because it is used to "tone up" other blacks.1 Bone black.-Ordinary bone black is made from bones charred in a retort. Coarsely pulverized, it is used for decolorizing sirups and oils. Large quantities are used in the refining of sugar, for which purpose it is more often known as bone char.2 Paragraph 447 of the tariff act of 1913 contains a provision for the free entry of bone black "not suitable for use as a pigment." The principal difference in the two forms of bone black is in the fineness of grinding, and the phrase "not suitable for use as a pigment" is not an accurate description of the article and has occasioned considerable litigation. (Reference should be made to the Tariff Information Survey on Bone Char and Blood Char, par. 447.) The bone black used as a pigment should be sufficiently fine that all of it will pass through a 250-mesh sieve. Some paint grinders require that over 99 per cent shall pass through a 350-mesh sieve. Sugar refiners, on the other hand, prefer bone black running from 16 to 30 mesh."

Drop black-So-called drop black is a bone black that is sold at a higher price because of the intensity of its color. The name comes from the former practice of grinding calcined sheep bones in water to an impalpable paste, which was then formed into cone-shaped drops. Drop black therefore became a synonym of a good black, and the name still clings to the finely powdered black now on the market. The composition is largely calcium phosphate, with only from 10 to 20 per cent of carbon.

(3) Charcoal blacks.-Charcoal from willow, maple, and bass trees is largely used as pigment in black paints. Many of these paints consist of charcoal, lampblack, litharge, and linseed oil. Such paints tend to solidify in the package (because of the litharge), but they are excellent preservatives for structural steel. Some charcoal is produced at paper mills, but the product contains up to 2 per cent of carbonate of potash, which unfits it for use in oil paints. Such material, however, is much used in the manufacture of oilcloth and coated leather.

Vine black. This pigment is in reality charcoal black that is made by charring grapevine. The grain is finer than ordinary charcoal and is denser. It is likely, however, to be too alkaline for general use with linseed oil.

(4) Mineral blacks.-Heavy black slate or shale is used to some extent in paint for buildings, but is used chiefly as black filler for ironwork. It is often toned with other blacks (carbon or lampblack) that are not so heavy, but the consumption is small because of its destructive action on paint mills and because its tinctorial

1 Black toner best serves its purpose in what is known as Black Color in varnish. Black paint composed of black toner ground in linseed and reduced with very high-grade coach varnish is worth (according to Toch) from $4 to $6 per gallon.

2 Blood char is also used for this purpose. These blacks, when imported, are free of duty and come under par. 447, act of 1913. (See p. 46.)

power is not high. Quite as satisfactory results are obtained by the use of fine silica tinted with lampblack, and at less cost. These blacks (mineral black, slate black, oil black, black chalk, etc.) are perhaps more important abroad than in this country and are found in abundance in Bavaria, Spain, Italy, and elsewhere.

Coal.-Powdered coal of various kinds is likewise used in some paints. It generally contains sulphur compounds, which are exceedingly harmful to metal and which prevent its being mixed with lead pigments. The use is not increasing.

Manganese ores.-Pyrolusite and hausmannite (natural oxides of manganese) are sometimes powdered for use as pigments, but their most important application in the paint trade is as driers in the preparation of boiled linseed oil.

Graphite, or crystalline carbon, both natural and artificial, is a very important paint pigment. Its extreme lightness requires that it be diluted with a heavier base to give it "tooth" and prevent it from being spread too thin. If used alone, 1 gallon of graphite paint will cover from 1,000 to 1,600 square feet of surface, or two or three times as much as most other pigments. Few graphite paints contain as much as 60 per cent graphite, since, in addition to its spreading too thin, it is also a slow drier.1

Asphaltum. Asphalts and bitumens are frequently used in the paint trade, although they are not strictly pigments. Natural asphalt may be considered as a mineral black, but there is no question of its being classified under pigments, as it is specifically provided for under paragraph 534 of the act of 1913.

(5) Black lakes.-Lakes of various kinds have been employed as black pigments. They are, however, of minor importance. Various coloring agents are used, including logwood decoction and potassium dichromate with copper sulphate, tannate of iron, and coal-tar colors. They are rapidly being displaced by black toners made from carbon blacks. These, however, are sometimes toned up by precipitating nigrosine (an aniline dye) on them. A high-grade black pigment is made by precipitating red, yellow, and blue aniline dyes upon the extract of ivory black, and this pigment is unusually flocculent and remains in suspension for a long time.

DOMESTIC PRODUCTION.

The total production of bone, carbon, and lampblack as reported by the census of 1914 was valued at $2,953,947. Approximately, one-half of this represents the value of bone black,2 one-third of it was carbon black, and one-sixth was lampblack. This figure does not include black pigments made and consumed by paint manufacturers and others, and marketed in the form of paint or other finished product, and which were not reported. It does include, however, the output of firms engaged primarily in the manufacture of fertilizers, paints, or varnishes. Such firms produced a total amount exceeding the output of all the establishments engaged primarily in the manufacture of blacks.

The Bureau of Mines 3 states that during 1918 the estimated production of carbon black was 43,500,000 pounds, of which 30,000,000

1 For further information in regard to graphite (plumbago), see separate unit of the Tariff Inf rmation Survey.

2 The Fuel Administration claimed that many of the West Virginia plants were extremely wasteful of gas, and several plants were closed as a war measure in 1917-18. 3"Carbon Black Industry Surveyed," by Roy O. Neal, chemical engineer, Bureau of Mines, The Chemical Engineer, April, 1920, pp. 121-3.