PROGRESS OF CHEMISTRY IN SOUTH LANCASHIRE. 121 



overcoming, and the process is now in full and successful operation at their 

 works at Warrington. With a most praiseworthy liberality, these gentlemen 

 have furnished us with full particulars regarding their process. They have 

 also allowed us to see it in operation, and we are therefore able to lay before 

 the Section all the details necessary for becoming acquainted with its prin- 

 cipal features. 



The only practical suggestion contained in Gay-Lussac's memoir, consists 

 in his proposal to convert cream of tartar by this method into oxalate of pot- 

 ash. At that time tartaric acid was cheaper than oxalic acid, and the sug- 

 gestion might therefore, under the circumstances of the time, have proved of 

 some practical value. It was evident, however, that for the purpose of ensu- 

 ring success a cheaper material had to be chosen. Messrs. Roberts, Dale 

 and Co. found woody fibre in the shape of sawdust to answer perfectly. Gay- 

 Lussac states, as the result of his experiments, that potash may be replaced 

 by caustic soda. Mr. Dale found, however, that woody fibre produces hardly 

 any oxalic acid with caustic soda. On the other hand, when potash is used 

 alone, the process is not remunerative. This difficulty was overcome by em- 

 ploying a mixture of soda and potash, in the proportion of two equivalents of 

 the former to one of the latter, which produces the desired effect quite as well 

 as potash alone. In what manner the soda acts in this case can only be con- 

 jectured : whether in conjunction with the potash it takes the place of the 

 latter, or whether it merely promotes the fusibility of the mixture, is merely a 

 matter for speculation. The solution of the mixed alkalies having been 

 evaporated to about 1*35 sp. gr., sawdust is introduced, so as to form a thick 

 paste. This paste is then placed on iron plates in thin layers and gradually 

 heated, the mass being kept constantly stirred. During the heating-process, 

 water is in the first instance given off. The mass then swells up and disen- 

 gages a quantity of inflammable gas, consisting of hydrogen and carburetted 

 hydrogen. A peculiar aromatic odour is at the same time evolved. After 

 the temperature has been maintained at 400° Fahr. for one or two hours, 

 this part of the process may be considered as complete. The whole of 

 the woody fibre is now decomposed, and the mass, which has a dark- 

 brown colour, is entirely soluble in water. It contains, however, only from 

 1^ per cent, of oxalic acid, and about 0*5 per cent, of formic, but no acetic 

 acid. What the nature of the principal product intermediate between the 

 woody fibre and the oxalic acid is has not yet been determined ; it seems 

 well worthy of further investigation. The mass is now exposed still longer 

 to the same temperature, care being taken to avoid any charring, which 

 would cause a loss of oxalic acid. When perfectly dry, it contains the 

 maximum quantity of oxalic acid, viz. from 28-30 per cent. (C^ O3 + 3 HO), 

 but still no acetic acid, and very little more formic acid than before. The 

 absence of acetic acid is surprising, as it is generally supposed to be an 

 essential product of this process of decomposition. It is possible that the 

 acetates may be converted into oxalates as they are formed ; but, on the other 

 hand Gay-Lussac states that acetates when heated with caustic alkalies yield 

 chiefly carbonates, and but a trifling proportion of oxalates — a conclusion to 

 which Mr. Dale has also been led from direct experiments with acetates*. 



The product of the heating-process, which is a grey powder, is in the next 

 place treated with water heated to about 60° Fahr. In this the whole dissolves, 

 with the exception of the oxalate of soda which is either contained in it, or 

 is formed by double decomposition on the addition of water, and which, on 

 account of its slight degree of solubility, falls to the bottom. The use of the 



* It may be mentioned that the process of decomposition takes place equally well in close 

 vessels. It must therefore be accompanied by a decomposition of water. 



