ON THE COMPOUNDS OF COTTON WITH THE ALKALIES. 17 IV.-On the Compounds of Cotton with the Alkalies. BY J. H. GLAD;STONE, PH D. THEbeautiful effects produced by Mr. Mercer through treating Gotton with a cold solution of caustic soda are well known not only to the scientific world but through the medium of the Great Exhi- bition to the public in general. Yet I believe the chemical compound tself has not hitherto been investigated. This gentleman found that when cotton or a cotton fabric is immersed in a very strong alkaline ley in the cold a certain com- bination is effected. This cCsodaed” cotton parts with all its alkali when washed with pure water and the “mercerized” cotton thus produced is not only milch contracted so that coarse fabrics have assumed the appearance of fine ones but when dyed it displays eolours of more than ordinary brilliancy.It is evident that by the processdescribed above the combination Qf soda and lignine is not obtained in a state fit for analysis. As the fabric issues from the alkaline ley there adheres to it an excess of soda and the momeiit it is touched by water its integrity is destroyed. It became a desideratum then to find a solvent capable of removing the uncombined alkali whilst it left the compound unimpaired. Alco-hol suggested itself to my mind as likely to possess the requisite quality especially as it might be employed in an anhydrous condition. As preliminary experiments two portions of pure cotton were taken each weighing 20 grs. when thoroughly dried.The one was steeped in cold caustic soda so dilute as not to produce Mr. Mercer’s re-action the other in a strong solution of soda. They were both soaked repeatedly in successive portions of absolute alcohol and subsequently dried in vacuo over sulphuric acid. In Exp. I. the cotton proved to be of the original weight and did not retain any soda; in Exp. 11. the cotton had increased to 24.4 grs. and con- tained an amount of soda which when dissolved out by water neutralized by sulphuric acid and evaporated in a platinum dish (excess of sulphuric acid in combination being removed as usual by small pieces of carbonate of ammonia) gave 4% grs. of sulphate= 2.1gra. of absolute soda. From the first experiment the conclusion may be drawn that absolute alcohol is capable of removing from cotton any portions of uncombined soda; and from the second it may be inferred that such alcohol does not decompose the compound of soda and cotton.VOL. 17.-NO. XVIT. c DR GLADSTONE ON THE Having thus obtained a method I performed a series of more exact experiments. A solution of soda of sp. gr. 1124 was found capable of combining with cotton though it did not produce much shrinking. It was made use of in preference to a stronger solu- tion as it left less alkali adhering to the fibre to be afterwards washed out with alcohol. Exp. 111. 20 grs. of cotton steeped for an hour in the alkaline ley washed repeatedly with absolute alcohol and thoroughly dried in vacuo had increased to 21.97 grs. and furnished 2.70grs.of sul- phate of soda. Exp. IV. The cotton regained from Exp. II. similarly treated showed an increase in weight to 21.09 grs, and yielded 2.71 grs of sulphate of soda. Exp.V. 20 grs. of cotton were treated in precisely the same man- ner but as the difficulty of washing out the uncombined soda consumed much absolute alcohol ordinary rectified spirits was employed instead. The soda compound weighed 21.28 grs. and yielded 2.05grs of sulphate of soda. Exp. VI. 20 grs. of cotton similarly treated were washed with hot alcohol of sp. gr. 825 The dried compound weighed 22.20 grs. and yielded 3.12 grs. of sulphate. This is a large amount and indi- cates that alcohol of this strength may safely be employed to wash the compound. Exp.VII. Lest it might be contended that the alcohol did not remove from the woody fibre certain impurities which might be present in an aqueous solution of soda 20 grs. of cotton were steeped in a clear but saturated alcoholic solution of the alkali. Little if any shrinking took place but there was a certain amount of COM-bination for the cotton well washed with spirits of sp. gr. 825 and dried weighed 21.01 grs. and afforded 1.41 grs. of sulphate of soda. As yet the results are very discordant as will be apparent from the annexed table nor does the combined soda in any instance stand in a definite atomic ratio to the lignin Ratio between original and soda-ed cotton and combined soda. 100 109.85 5.91 100 105*45* 5.94 100 106*4 4-49 ? VI* 100 111.0 6.83 , VII.100 105.05 3.08 * This number is reckoned as obtained from 20 grs.; but it is in all probability too low since the whole amount of cotton as will be afterwards explained is never reco-vered from the mercerizing process. COMPOUNDS OF COTTON WITH THE ALKALIES. Prom this we must conclude either that woody fibre has a great affinity for caustic soda at a low temperature but does not form any definite chemical compound with it; or else that the cotton in the forementioned experiments had not been thoroughly saturated with the alkali. As this might depend upon the strength of the alkaline ley in which the immersion was made a solution of soda of sp. gr. 1342 was employed and Save much more satisfactory results. Exp.VIII. 20 grs. of cotton steeped in soda-solution of the above- mentioned specific gravity and washed with successive portions of hot alcohol of sp. gr. 835 until when dried it ceased to lose weight was found to have increased to 22.64 grs, and yielded 4.25 grs. of sulphate of soda. Exp. IX 20 grs. of previously mercerized cotton similarly treated showed an increase of weight to 23.21grs, and yielded 4-70grs. of sulphate. -Exp. X. A piece of calico 4 in. x 4 and weighing when tho- roughly dried 18.65 grs. was subjected to the action of soda. From a solution of sp. gr. 1124 it absorbed an amount of soda equivalent to 2.00 grs. of sulphate; that is as 100 :4.70 combined soda. Washed with water dried again immersed in alkaline ley but of sp. gr. 1342 washed with hot alcohol of sp.gr. 835 and dried in vaeuo it weighed 21.84 grs, and yielded 4-44) grs. of siilphate of soda. The immer- sion in soda only lasted 10 minutes. The piece of calico had con- tracted to the measure of 3.3in. x 3.3. Exp. XI. In order to ascertain whether the fibre was capable of combining with a still larger proportion of soda either by employing a stronger alkaline ley or by exposing it to the action for a longer period a piece of calico weighing 18-32grs. was immersed for 17 hours in a solution of caustic soda so strong as to be syrupy in a vessel protected from the atmosphere. Having been washed and dried as usual it weighed 21.04 grs. and yielded 3.78 grs. of sul- phate of soda. This instead of being a larger amount of soda than in the three previous instances is a trifle smaller.There was the same amount of contraction. Exp. XII. was intended as one in which every precaution should be taken to insure the definite character of the compound examined. A piece of fine calico of about 90 strands to the inch weighing 14.67 grs. and measuring 3 in. x 3 was steeped in cold caustic soda in a close vessel for 30 minutes. It was then removed pressed between folds of cloth and washed with absolute alcohol also in a vessel pro- tected from the air until it ceased to lose weight when dried. Dried c2 DR. GLADSTONE ON THE in vacuo it weighed 17.17 grs. and it afforded 3.15 grs. of sulphate of soda. The results of these five experiments may be thus tabulated Ratio between original and soda-ed cotton and combined soda.100 1132 9.31 100 116.05 10.30 100 111.2 10.34 100 114.8 9.07 100 117.05 9.41 It will be at once evident that there is a wide discrepancy between the numbers in the first column but the second column presents con- siderable accordance; and if we take the amount of soda in the experiment most to be relied on-No. XII. namely 9-41 per cent or the average of the whole five determinations,-namely 9.68 per cent we find it almost exactly coinciding with the amount that should be obtained supposing one atom of soda to combine with one atom of lignine-C2 H, O,,-namely 9.65. 324 31.3 100 9-65. The mode of production of this substance might lead us to imagine that it was a substitution product of C, H, 020, in which one equiva- lent of sodium replaced one equivalent of hydrogen; but as the weight of the dried substance never fell short of the united weights of the cotton and the soda taken up it must rather be considered as a compound of the two.The difference of its state of hydration clearly gives rise to the differences observable in the first column of the tables. In some instances (as Exp. X.) the soda appears to carry along with it little or no water in other instances (as Exp. XII.) as large a quantity as 3 equivalents; and this combined water will not separate in vacuo at ordinary temperatures. The compound is also very hygroscopic absorbing from moist air in one observed instance as much as 5.39 grs.of water for 23.21 grs. of “ soda-ed” cotton which however it parted with again in vacuo. When iieutralizing with sulphuric acid the soda washed out from the cotton I had fre- quently observed that there was no effervescence this induced me to try whether the ‘‘soda-ed” cotton really did not absorb carbonic acid. Upon exposing a portion to an atmosphere of this gas I found the alkali was converted into carbonate; and 20 grs. of cotton which proved to be combined with 2.06 grs. of soda weighed when dried in vacuo 23-71 grs Little or no water could have been retained by the COMPOUNDS OF COTTON WITH THE ALKALIES. substance for the weight of the cotton plus that of the alkali consi- dered as carbonate would be 23.51 grs. There is a remarkable circumstance attending this compound in its relation to heat it becomes scorched at a far lower temperature than the original cotton.That the combination of the soda with the cotton has effected a permanent change upon it is certain; when regained it is contracted and takes dyes better; but the question arises Is this merely a physical alteration or has a real chemical change of the lignina taken place ? I am inclined to view the ‘‘mercerized” cotton as chemically identical with the original sabstance. In the first place it is of the same ultimate composition. It is true the cotton regained never absolutely equalled the original in weight ;but it was always observed that the fibre lost some flocculent portions during the steeping and the washine rocesses enough to account for the 1 or 1.5 per cent b? deficiency which usually occurred.The removal of only one equi- valent of water would have occasioned a decrease of 2.78per cent. Again the mercerized cotton can be recombined with soda causing even some additional shrinking by the process. Mixed nitric and sulphuric acids convert it into gun-cotton; it is acted upon by oil of vitriol just as ordinary lignine ; and it is similarly hygroscopic. The change that takes place in the physical condition of the cotton is best observed under the microscope. The fibres in their ordinary state appear as flattened twistedribands; but the moment they are touched by the alkaline ley they untwist themselves and contract in length as they swell out assuming a rounded solid form; and this circular appearance they retain after the soda is removed by water.Thus the shrinking is explained and I think also the superior character of the colours which mercerized cotton is capable of exhi-biting. For the substance of the fibre itself is of a porous nature and will of course absorb a larger quantity of the dye when expanded than when compressed into a flat twisted band and as this takes place in the same space a greater intensify of colour must be the result. From these observations it appears that lignine is capable of forming a combination with soda the proportion of the alkial varying with the strength of the solution employed but in no instance exceeding olie atom and that this compound is decomposed by water being resolved into its original compounds.In order to ascertain whether a similar potash compound existed a piece of fine calico measuring 3 in. x 3 and weighing 14-50grs, was immersed for thirty minutes in a8 strong a solution of potash as MR. ROWNEY ON THE OCCURRENCE OF could be obtained limpid. It was washed with alcohol of sp. gr. 825 and dried and decomposed as usual. It shrank to the dimensions of 2.7 in. x 2.7. Whcn combined with potash it weighed 17-14!grs. and it yielded 3.83 grs. of sulphate of potash. Ratio between original and combined cotton and potash. Exp. XIII. . . . 100 118.2 I 14.27 This shows that there was one equivalent of potash taken up by the cotton the compound being C, H, 0, +KO. 324 :47.3 : 100 14.59.These compounds of the alkalies with lignine are clearly analogous to their known cornpounds with sugar. Brendecke and others have shown that both cane- and grape-sugar will combine with potash and soda in the proportion of 1 equivalent C, H, 02*, to 1equivalent of the alkali. Whether these compounds are decomposed by water does not appear from the recorded observations; for whether it be so or not the same phenomena would be presented. Disregarding the varying amount of water combined with the lignine compounds we find both them and the sugar compounds expressed by the formule C, H, 020. KO and C, Nzo02,. NaO.