PROGRESS OF CHEMISTRY TN SOUTH LANCASHIRE. 125 



mostly made and consumed by printers themselves), is estimated at about 

 1200 tons per annum, which would require about three times its weight of 

 madder for its production. 



Of the second class of inventions bearing on madder, perhaps the most 

 successful is that which was patented by Pincoffs and Schunck in the year 

 1853. It is well known that in order to produce the finer descriptions of 

 madder colours, such as pink and lilac, on cotton fabrics, it is necessary 

 to subject the dyed goods to a long series of operations, such as soaping, 

 adding, &c. These processes are always attended with some risk of failure; 

 and besides that, a very large quantity of madder (an excess, in fact) must 

 be employed in dyeing, in order to obtain the ultimate effect desired. It is 

 evident that, if the impurities (resins, pectine, &c.) accompanying the 

 colouring-matters in the root could be removed or destroyed, the opera- 

 tions necessary after dyeing might be dispensed with or much curtailed, 

 since the object of these operations is precisely the removal of these im- 

 purities from the dyed fabric. lu the preparation of ordinary garancine 

 a portion of these impurities is removed, but those which are insoluble, 

 or difficulty soluble in water, remain behind for the most part, and subse- 

 quently exert a prejudicial effect in dyeing. Now the invention referred to 

 above consists in subjecting garancine whilst in a moist state to the influ- 

 ence of an elevated temperature in close vessels (or what comes to precisely 

 the same thing, to the action of high-pressure steam) for several hours. 

 What takes place during this process is not exactly known. According to 

 some experiments undertaken by one of us, if appears that the two red 

 colouring-matters contained in madder, viz. alizarine and purpurine, are not 

 in the least degree affected by it, whereas the pectic acid and some of the 

 resinous colouring-matters are charred, and thus rendered insoluble and inno- 

 cuous. Be this as it may, the result of the process is a product which, when 

 used for dyeing, yields colours requiring very little after-treatment in order 

 to give them the required degree of brilliancy, whilst they are quite as per- 

 manent as those produced by madder itself. The use of this material is 

 attended by a saving in dye-stuff, mordants, and soap, as well as in time and 

 labour. The results are also more certain. Moreover, when other colours, 

 such as brown and orange, are introduced in combination with madder colours, 

 the effect is much superior to that produced with madder, where the soapings 

 required to yield the desirable brightness deteriorate tlie other colours. 

 There are other advantages of a practical nature attending its use which 

 need not be here referred to. It has, however, one disadvantage, viz. that from 

 some unexplained cause it is not well adapted for dyeing pink ; and for this 

 colour it is therefore still necessary to employ unprepared madder. The pro- 

 duct has obtained the name of Commercial Alizarine, since the effect in dye- 

 ing is similar to that of the pure colouring matter, alizarine. It is manufac- 

 tured on a large scale by Messrs. Pincoffs and Co. Since its introduction in 

 1853, more than three million pieces of calico have been dyed with it in our 

 district and in Scotland. 



Mr. Higgin prepares commercial alizarine by boiling garancine with water, 

 carbonate of soda, and a little ammonia. The liquid, which is alkaline at 

 first, is boiled until it becomes acid. A short boiling gives a garancine 

 adapted for dyeing purple, whilst a boiling of twenty-four hours yields aliza- 

 rine. 



We may here mention Messrs. Roberts, Dale and Co.'s process for pre- 

 paring lakes, as the compounds of organic colouring-matters with various 

 bases are usually called. Such lakes, with a basis of alumina, have for a long 

 time been made from peachwood, sapanwood, and other dye-woods; but 



