John L. Crist was one of the founders of Beaver Chemical.  This article was
published in the American Dyestuff Reporter, Vol. 16, No. 13, August 8, 1927.
In this paper it has been decided to refrain from a purely technical discussion and to treat the subject of the manufacture of
sulphur dyes in a general and rather practical matter.  Sulphur dyes have been generally regarded and for the purpose of this
paper will be considered as those dyes which are applied to the fiber by the aid of the alkaline sulphides, the most common,
and, in fact, the sulphide of universal use being the well- known sodium sulphide of commerce.

The means of manufacturing sulphur dyes were discovered late in the ‘90’s, and this class of dyes first found general and
favorable use from 1900 to 1910, after overcoming much prejudice which many present will easily recall.

For the sake of clarity the manufacture of sulphur dyes has been divided into two main subdivisions.  First, that class of sulphur
dyes that are manufactured by the baking, roasting or so-called dry fusion process.  A few examples of this class are the Sulphur
Browns, Sulphur Tans and Crutches and Sulphur Yellows of the redder shades.  And second, that class manufactured by the so-
called wet fusion process, a few typical examples of which are Sulphur Blacks, Sulphur Navy, Sky, and Brilliant Blues, Sulphur
Bordeaux and Sulphur Green.  In general, subject to certain exceptions, the cheaper and duller dyes are made by the dry fusion
process, some of which, however, have exceptional fastness and good working qualities, and the brighter more expensive
shades are produced by the wet or aqueous fusion process.

One typical shade or type has been selected from each of these general classes for rather detailed study.  From the dry process
class Sulphur Yellow of the soluble reddish type largely used in combination for producing khaki shades has been selected, and
from the wet fusion class the well-known Sulphur Navy Blue has been selected as typical.



An outline of the process for manufacturing Sulphur Yellow of the reddish type is as follows:

Certain definite amounts of sulphur, meta-toluene-dyamine or the  formyl, diformyl and aldehyde derivatives of meta-toluene-
dyamine and benzidine are heated in an iron pot, kettle or mixer to about 300 deg. Cent. or 575 deg. Fahr. for a period of time
about 12 to 30 hours.  During this process hydrogen sulphide is evolved and towards end of the reaction the mass becomes
quite thick.  At this point in the process the semi-fluid mass is sometimes transferred to pans, and the process carried to
completion by continued heating at higher temperatures in a so-called baking oven, constructed in general along the lines of a
bakery oven in an ordinary kitchen range or a commercial bakery.  The baking process is usually carried on with the exclusion of
air to prevent combustion of the dyestuff, until the mass becomes quite stiff.  When the reaction is considered complete the
furnace is allowed to cool, whereupon the mass becomes quite hard and brittle.

Formerly quite a number of tans and browns were taken at this point and merely ground to the desired fineness, blended with
salt for standardization and marketed in the crude state.  Even now some of the cheaper dark browns and tans are found on the
market prepared in this way.  However, the best practice is to insure a uniform product with the minimum of insoluble matter is to
dissolve this mass in a solution of sodium sulphide or caustic soda, filter the solution and precipitate the refined dyestuff from
the solution by the use of an acid and acid salt or by blowing air through the dilute solution to oxidize the sulphide.  The liquor
containing the dyestuff in suspension is then filtered, the precipitated dyestuff dyed, ground, blended with salt, sodium sulphate,
etc., to standardize, and marketed.

We will now take up in a general way the manufacture of Sulphur Navy Blue as representative of the wet fusion process class.

The first step in this process is the preparation of para-nitroso phenol, which is formed by the action of sodium nitrite on phenol
(carbolic acid) in an acid solution at a temperature of near 0 deg. Cent.  This para-nitroso phenol is filtered, wrung in an extractor,
analyzed and stored in a cool place.  It is quite combustible and inflammable, and great care must be used in handling and
storing it.

The second step is the preparation of the color base or the indo-phenol by the condensation at low temperatures in a solution of
sulphuric acid of the para-nitroso phenol and ortho-toluidine.  When this extremely delicate reaction is complete, the mass is run
into a dilute solution of soda ash and the acid neutralized with the resultant precipitation of the indo-phenol which is filtered and
analyzed but not dyed, as the color base is quite unstable and must be used fresh.

The third step is the preparation of a sodium polysulphide by heating together certain quantities of sodium sulphide in solution
and sulphur.  The indo-phenol is then dissolved in the sodium polysulphide, the solution brought to a definite boiling point by
evaporation or dilution and run at boiling in a closed tank or kettle equipped with a reflux condenser for a certain period from 12 to
100 hours until reaction is completed.  During the fusion cycle there is quite an evolution of hydrogen sulphide.  The strength of
the polysulphide, the proportion of sulphur to the sulphide, the temperature and the time of the fusion reaction are all varied to
produce the desired shades.  Also certain solvents and fusion assistants are sometimes employed to produce certain shade or
solubility results.  Among these assistants are alcohol, glycerine and their derivatives.

The fourth step consists of diluting the completed fusion and precipitating the dyestuff from the sulphide solution by means of
acid, acid salts, or by blowing air through the solution to oxidize the sulphide.

The fifth step consists of filtering the precipitated dyestuff drying, grinding, aging and standardizing by blending various batches
and reducing with salt, sodium sulphate, etc., and marketing.

It is quite essential in almost all classes of sulphur dyes to give them an aging process after the finished dyestuff is dried.  This
is to permit the dyestuff to take up from the atmosphere the desired amount of moisture and oxygen to become more stable in
this respect; otherwise the change goes on after standardization, resulting in an “off standard” dye, and is some cases when the
barrel is opened and the dyestuff permitted to come in contact with the air a rapid oxidation takes place with the resulting firing of
the dyestuff in the barrel.

The kind of water used in the various manufacturing processes also exerts a powerful influence on the shade and solubility of
the dye.  In general, the purer the water the more soluble and brighter the dye.  Soluble metallic salts in the water exert a very
harmful influence.

Lead, iron and wood are the principal materials of which the apparatus is constructed.  Iron is nearly always preferable owing to
its low cost and permanency where its use is permitted.  Some dyes are very sensitive to iron, in which cases it is necessary to
resort to other metals.  Certain sulphur dyes that are sensitive to iron can be produced in lead apparatus, and when dyed in
glass or porcelain dye pots in the laboratory give brighter shades.  However, when dyed in iron machines the shade is materially
affected so that most of the apparent advantage of the lead apparatus is lost.  Others are not so sensitive to iron in dyeing and
lead or lead lined apparatus is quite desirable.  Copper or brass must be avoided around the sulphide fusion kettles, as the
copper is readily affected by the sulphide.  Also wrought iron and steel are more resistant to sulphide than cast iron.

The most desirable location for a factory to make high grade sulphur dyes is:
1)  Where an abundance of pure water is available.
2)  Where sewage disposal can be readily affected and where obnoxious fumes are not prohibited.
3)  Where high grade intelligent labor is available.
4)  Where the source of raw material is near and where the market for the product is sufficiently close to avoid too much delay in
shipping the product.  The amount of raw materials used exclusive of fuel is often about 8 to 10 times the weight of the finished
dyestuff.  Therefore, the proximity of the factory to the source of supply of the chemicals is more important from the standpoint of
transportation than to be close to the consumer.  However, the question of service to the consumer must have serious
consideration.
5)  Where power or fuel or both are cheap.
6)  Where the climate is not too rigorous to prohibit the use of lightly constructed buildings, as light and ventilation are prime
essentials.


We have covered a general outline of two typical processes of the two general classes of sulphur dyestuffs, also some generally
related factors.  Now from the time the process for the first intermediate is begun until the dyestuff is in the barrels in a dry
warehouse the factors of proportions of the various chemical ingredients, the factors of time, temperature, concentration,
agitation and other plant conditions must be controlled within very narrow and predetermined limits.  All these factors have a
direct bearing on the properties of the dyestuff, such as shade, strength, solubility, uniformity, fastness, property of changing
much or little on oxidizing and after-treating, and, in fact, practically all the properties of the dyestuff are subject to and controllable
by the various factors above mentioned.  During all these processes accurate laboratory control must be maintained as a check
on and a guide to the plant procedure.  This includes analyses of raw materials and intermediates and a constant checking of
finished batches regarding all their properties.

Of all the classes of dyestuffs, the sulphur dyes, because they are in most cases not definite chemical individuals but mixtures of
many, are most susceptible to plant factors and conditions, and consequently they require the greatest amount of care in their
preparation.  It might be said that the single greatest factor contributing to the manufacture of a high-grade sulphur dye is eternal
vigilance all the way down the line.  

It is difficult to pass from the subject of manufacturing without touching on the testing of the dyestuff in the laboratory of the
producer, and likewise in the laboratory of the dealer or sales agent and the consumer.  Almost all sulphur dyes are
undetermined and undeterminable mixtures of various related chemical individuals, and very few are definite chemicals
themselves.  Also the properties of fastness and solubility, properties of being reduced and oxidized, properties in respect to
aftertreating and exhaustibility are all strictly relative properties.  Therefore, with so many variables it is essential that the
producer, the agent and the consumer all follow the same testing procedure to the minutest detail if comparable results are to be
expected.   The producer should know the use to which his product is to be put, and all parties concerned should adjust their
dyeing and testing procedure to the closest approximation of the consumers’ conditions as is possible to do so.

It is of greatest importance to the manufacturer and also of great mutual benefit to the consumer when the manufacturer can
know to what use his product is to be put by the consumer.  Only in this way can the best results be secured by both, for the
manufacturer, knowing certain mill conditions, can often change his processes so as to give to a certain color certain qualities
that are especially desirable under given mill conditions, whereas, had he not known these peculiar conditions, his product,
while suitable for most conditions, might be unsuited to this particular condition.  In this event neither the manufacturer nor his
product nor the consumer nor his conditions are to be wholly blamed; ignorance and unwillingness to co-operate are the causes
of most troubles along this line.

The manufacturers observe with unmixed gratification the constantly improved personnel in the dyehouses, and he looks forward
to the time when all dyehouse superintendents will be technical experts trained in the application of dyes and related subjects.

May we all-manufacturers, dealers, agents, dyers and consumers-work and pray to the end that the time will soon come (and let
us do our part to hasten it) when there will exist a complete spirit of co-operation and helpfulness between consumer and
manufacturer, and a mutual willingness and desire to go to the bottom of our mutual troubles before blaming some product or
condition, when in most cases our troubles can be eliminated or minimized by intelligent co-operation.

*A paper read before the joint meeting of the South Central and Piedmont Sections of the American Association of Textile
Chemists and Colorists at Asheville, N.C., July 16, 1927.
The Manufacture of Sulphur Dyestuffs
ColorantsHistory.Org
The Manufacture of Sulphur Dyestuffs*
By John L. Crist
Manager, Beaver Chemical Corporation, Damascus, Va.
How Sulphur Yellow Is Made
Need of Accurate Control