John Dale (Chemist)
Born in Birmingham, 11 May 1815.
Died 1889.
Obituary [1]
'By the death of John Dale technical chemistry has lost one of its foremost pioneers, who was acknowledged as such on the Continent and in America as well as in the United Kingdom. Dale was a born chemist ; a man may be taught chemistry, but he never will distinguish himself as a chemist, if he does not possess an enthusiasm for the science, and this Dale had in the highest degree. He was born at Birmingham, on the nth of May, 1815, and educated in his native town, and in Warwick. In the latter place he had a schoolmaster of whom he always spoke with great admiration. This excellent man took his pupils out for a walk, asking questions on all natural objects they came across, and at the same time giving them instructions. To this original and attractive mode of teaching. Dale attributed much of the acuteness and power of observation by which he was distinguished. After his school days, Dale was apprenticed to a chemist and druggist at Denbigh, and from there he moved to Rhyl, where he had access to a number of chemical and pharmaceutical works, which enabled him to prosecute his studies. We next find him in Manchester as assistant to Mr. Ansell, a member of the Society of Friends and an acquaintance of Dalton, with whom Dale also soon became acquainted, and from being his pupil he became his friend. Following the example of his master, Dale commenced a course of lectures on Chemistry, going to all the principal towns of Lancashire. He illustrated his lectures with many original experiments, which he performed most skilfully, and received from Dalton especial commendation and compliments on his successful undertaking. He often related with great humour, how after a lecture in a school-room, he gave orders to have the room locked until he could remove his apparatus and chemicals. The schoolmaster being struck with the combustion of phosphorus in oxygen, could not resist the temptation to carry off a piece of this dangerous body, which had very unpleasant consequences, as he put it in his pocket for taking it home. After a short removal to Altrincham, Dale returned to Manchester, where he took a shop in St. Mary's Gate, and during this period he made the acquaintance of Mr. T. Roberts, with whom he afterwards went into partnership. It was at this time that he made his first discovery. In 1825 Faraday had been requested by the Portable Gas Company to find out why the gas, which was obtained by the distillation of oil and pumped into copper cylinders under pressure, lost much of its illuminating power when kept for some time. Faraday found the cause to be the condensation of some of the gas to a liquid, which he examined and thus discovered two new hydrocarbons. One of these, which he called bicarburet of hydrogen, was in 1834 obtained by Mitscherlich from benzoic acid and named benzine by him, on the assumption that it was derived from benzoic acid simply by the abstraction of carbonic acid. To this Liebig objected, and changed the name of the empyremnatic oil obtained by distilling benzoic acid with lime into benzol, because the ending ine reminded one of quinine or strychnine with which it had nothing in common. He adds that it would have been better to have retained Faraday's name, as this oil had no closer connection with benzoic acid than with train oil or coal from which it also might be obtained. How Liebig became acquainted with the fact that benzene is formed by the dry distillation of coal is not known, as his pupil Hofmann, who obtained it in 1845 from coal-tar observes : "It is frequently stated in memoirs and text-books that coal-tar oil contains benzol. I am, however, unacquainted with any research in which this question has been investigated."
'The writer, taking an interest in this question, asked Mr. Dale if he could give him any information, and thus elicited the following interesting facts. About 1834, at the time when Mitscherlich had converted benzol into nitrobenzol, the distillation of coal-tar was carried out on a large scale in the neighbourhood of Manchester ; the naphtha which was obtained being employed for the purpose of dissolving the residual pitch and thus obtaining a black varnish. Attempts were made to supplant wood-naphtha, which at that time was used in the hat factories at Gorton for the preparation of " lacquer " by coal-tar naphtha. The substitute however did not answer, as the impure naphtha gave off on evaporation so unbearable a smell, that the workmen refused to employ it. It was also known about 1838 that wood-naphtha contained oxygen, while that from coal-tar did not, and hence Mr. Dale attempted to convert the latter into the former, or into a similar body. By acting on it with sulphuric acid and nitre, he obtained a liquid possessing the smell of bitter almonds, which, however, he did not examine any further. This was done by Mr. John Leigh, who, at the meeting of the British Association held in Manchester, 1842, exhibited a considerable quantity of nitrobenzol and dinitrobenzol before the Chemical Section, Dalton being the president. Thus, for the first time, it was proved that coal-tar contains a considerable quantity of benzol. Liebig was in England at this time, and, if the writer IS not mistaken, attended the Manchester meeting, and when he in 1834 said that benzol could be obtained from coal, he most probably arrived at this conclusion because the products of the distillation of oil are very similar to those obtained from coaL
'From the shop in St Mary's Gate, Mr. Dale went as manager to a print-works in Ardwick, and the knowledge of printing and dyeing which he thus acquired became of the greatest use to him afterwards.
'In the year 1852 he started, with Mr. Roberts, the well known chemical works at Cornbrook, and soon introduced many new processes of manufacture. The paper-hanging trade began to develop at this time, and Dale replaced the older colours by much brighter and finer ones, such as a much superior class of chrome-yellows and of lakes, as the compounds of organic colouring matters with certain metallic oxides are called. Such lakes, with a base of alumina, had for a long time been made from sappan-wood, peach-wood, &c. ; but they had several disadvantages, which restricted their use in practice, not being permanent and having little body. Moreover, they were gelatinous and cracked on drying. Mr. Dale avoided this by using oxide of tin as a base, and thus produced lakes which, owing partly to their physical condition, and partly to their chemical composition, possessed the requisite degree of permanency and intensity of colour. Of these a beautiful scarlet lake from bar-wood may be specially mentioned, because it is obtained by a method which could only have been devised by a practical calico printer. The colouring matter of bar-wood is very slightly soluble in water ; the ground wood is, therefore, simply treated with boiling water and the required quantity of oxide of tin is added, which absorbs at once the colouring matter as soon as it gets into solution, and thus more and more dissolves and combines with the oxide until the lake has acquired the requisite intensity of colour and the wood is exhausted.
'Dale's greatest achievement was, however, the manufacture of oxalic acid from saw-dust. Up to this period it was -obtained by oxydising sugar or starch with nitric acid. Gay-Lussac had already shown in 1829, that this acid is also produced by heating vegetable fibre, sugar, starch, gum, and tartaric acid with caustic potash. Neither scientific chemists nor practical men attended to this subject until Mr. Dale took it in hand. In his attempt to do so, he was met with a number of serious obstacles, chiefly of a practical nature. These, however, he, by dint of uncommon ingenuity, and by the application of an amount of perseverance of which, perhaps, but few men are capable, succeeded in •overcoming, and the process was then soon in full and successful operation at Messrs. Roberts, Dale, and Co.'s works, at Warrington. None of the scientific chemists who attended the Manchester Meeting of the British Association in 1861, when Kekule was his guest, will forget the day when Mr. John Dale conducted them over the works and explained the process to them in his peculiarly lucid manner. The only practical suggestion which Gay-Lussac had made consisted in the proposal to convert cream of tartar by his method into oxalic acid. At that time tartaric acid was cheaper than oxalic acid, and the suggestion might, therefore, under the circumstances of the time, have proved of some practical value. It was evident, however, that for the purpose of ensuring success a cheaper material had to be chosen. Dale found woody fibre in the shape of saw-dust to answer perfectly. Gay-Lussac had stated that potash might be replaced by soda ; Mr. Dale, however, found that saw-dust yields hardly any oxalic acid when fused in the soda. On the other hand, potash was found to be too expensive, and the process would not pay. He overcame the difficulty by using a mixture of two equivalents of soda to one of potash, which answers not only as well as potash alone, but has the great advantage, that an almost insoluble sodium oxalate IS formed, and thus the excess of alkali and all the bye products can be easily separated. For a successful operation of the process it was necessary to bring the recovered mixture of the alkalis quickly into work again, which could be only done by having a rapid method for determining their relative amount A series of experiments led Dale to a very simple method of analysis. A given volume of the solution is neutralized with tartaric acid of known strength, and then an equal volume of the latter is added in order to convert the alkalis into the bitartrate, that of potash separating out and the separation is quickened by stirring the liquid well. In order to get good results the solution of the sodium bitartrate must be nearly saturated or stand at 6° Tw. The cream of tartar which separated out was filtered off, slightly washed with water, and filtrate and precipitate were then separately neutralised with a standard solution of caustic soda. Thus the percentage of the two alkalis could be ascertained within half an hour. Dale, as usual, did not publish this method, and many years afterwards it was rediscovered by Mohr.
'The same was the case with another analytical method which Dale devised for estimating the amount of colouring matter in indigo, which is called indigo blue and has the characteristic property of being converted, by reducing agents, into indigo white, which is soluble in alkalis. On exposing this solution to the air, it rapidly absorbs oxygen, and indigo blue is reprecipitated. This reaction is made use of in indigo dyeing, fine indigo being brought together with water, green vitriol, and slaked lime. A careful examination of this subject by Dale showed that a certain quantity of indigo blue undergoes such a change that it is not reprecipitated, and in employing this reaction as an analytical method, this has to be taken into account. By a series of elaborate experiments Dale found that by working under strictly the same conditions, the loss is quite constant, and thus he discovered a method by which the value of indigo can be quickly and exactly determined. This method was communicated to the writer by Mr. Dale and published in the second edition of Muspratt's dictionary.
'Ullgren later came to the similar conclusions as Dale and published a paper on the subject in Liebig's Annalen,
'Other analytical processes were devised by Dale, as that for estimating tin by potassium dichromate, and his fertile and resourceful mind led him to many other improvements in technical and analytical chemistry. In the year 1858 Perkin discovered aniline-purple, or mauve, the first aniline colour which appeared in the market. He obtained it by the action of potassium dichromate on sulphate of anilin. Dale, in conjunction with Caro, endeavoured to find an equally effective oxidising agent, and both having a practical acquaintance with calico-printing, hit upon one which a purely scientific chemist would probably not have thought of They employed a mixture of copper sulphate and common salt By using this, however, acid was liberated which interfered with the production of the colouring matters, and the further improvement of the process which Dale devised was a judicious addition of an alkali. At the same time a useful black pigment was produced, which is the more interesting as it may be said to have led to the discovery of aniline-black by Lightfoot, to whom the reaction was known.
'Among the artificial colouring matters which to-day are largely manufactured, the class of the azo-colours is one of the most important. Of these in 1863 only aniline-yellow was known. Dale, in conjunction with Caro and Martius, soon brought two new ones, known as Manchester Yellow, or Martius Yellow, and Manchester Brown, or Bismark Brown, which are still specialities of Messrs. Roberts, Dale and Co. Many other novel and original processes were devised by Mr. Dale, who was always ready to place his large and unique experience at the disposal of his friends, and among these the writer has to thank him for much and most valuable information. During the last four or five years his health had been failing, but his interest in the later development of technical and pure science never flagged. He died 31st May, 1889, and thus another link of the chain connecting the younger generation of chemists with the illustrious Dalton has been broken.'