hair, because the potash unites with the grease on the hair to form a soluble soap, which is quickly removed by rinsing the hair in clean water. III.-BLEACHING AND DYEING. As to the nature and use of bleaching agents. Our knowledge as to the chemistry of bleaching is still very imperfect, despite the great strides made in chemical knowledge during the present century. In spite of the grand array of facts that have been amply demonstrated to us by different chemists during the last hundred years, in the matter of the action of bleaching agents there is still much room for doubt and a fair field for theory. When, however, all our theories have been ventilated and all our doubts expressed, there yet remain two well defined principles, one or the other of which seems to underlie most processes of bleaching, and by which nearly all, if not quite all, may be explained. The destruction of color, the formation of white compounds from colored ones-that is to say, bleaching-usually results from either oxidation or reduction. In the case of oxidation the coloring matter unites, either directly or indirectly, with oxygen, and in so doing is destroyed as such; in the case of reduction the color matter unites with hydrogen to form a white compound. The practice of bleaching by exposure to air, moisture, and light may be traced back to very early times, but owing to the pressure of population, it is not nearly so extensively followed now as formerly. In cities like London, where the space is very limited and where the air contains the minimum amount of oxygen (O), with no ozone (0) at all, and the maximum amount of atmospheric impurities, bleaching by simple exposure is attended by so many difficulties as to be wellnigh impossible. Now and again in country gardens you may see small grassy plots set aside for the family clothes-bleaching, and here and there you may find whole tracts of meadowland given up to the bleacher, but in England this is much more rare than in sunnier lands; there, after white clothes are washed and dried, they are taken from the line, spread out on a well swept plot of grass, watered from the watering-can, and bleached in the sun. As this is done regularly with every wash the clothes rarely get yellow, even when they are old and much worn. This process of bleaching by exposure to air, light, and moisture, is doubtless in part due to oxidation, but oxidation in its mildest, gentlest form, unaccompanied by the violent action which is found with so many bleaching agents and which results in the destruction of the fibres of the cloth. The fading of colors in the sun is, of course, only another expression for bleaching by exposure. Some colors form white compounds with atmospheric oxygen more easily than others, and such colors are said to quickly fade. Of all oxidizing agents used for bleaching purposes chlorine (Cl) is perhaps the most widely used. Dry chlorine has no bleaching properties, but in the presence of moisture color is very quickly destroyed by it. Moisture, or water, is a compound of oxygen and hydrogen (see Vol. VI., page 291); chlorine has a very strong affinity for hydrogen, stronger even than the attraction of oxygen for hydrogen; therefore when chlorine finds itself in the presence of any moisture it ousts the oxygen from its place in combination with the hydrogen, Bleaching powder is a compound of calcium, chlorine, and oxygen (Ca Cl2 + Ca [O C1]), sometimes called hypochlorite of lime, but more usually chloride of lime. Different theories as to the constitution of the compound have been put forward at various times, but I think none as yet been finally accepted as the right one. To discuss these theories now would be altogether beyond the limits I laid down in commencing this series of papers, and would not be likely to answer any useful purpose. It is sufficient for us to remember that whatever may be the true constitution of bleaching powder, it certainly contains calcium, chlorine, and oxygen. An acid acting on this substance liberates the chlorine, and the chlorine in turn sets free the oxygen from any moisture present, and this liberated oxygen oxidizes and destroys any organic color-matter with which it may come in contact. The bleaching of cottons by bleaching powder is a work requiring great care. When the operation is properly carried out, all color heretofore present is destroyed, leaving the fibres of the cloth uninjured. The process of bleaching on a large scale is stated to be somewhat as follows: The cloth is boiled with milk of lime, to remove any resinous matters present in the fibre; it is next washed with water and scoured with very dilute acid, to cleanse the cloth from the lime, and again washed to remove the acid. The cloth is then boiled in a dilute soda-lye, which clears away the dirt and fatty matters. After this comes the "chemicking"; that is to say, the cloth is again washed and steeped in a dilute solution of bleaching powder, scoured with dilute acid, washed, and dried, and this completes the process of bleaching. When any of the prepared bleaching powders (there are several, but the best known is the chloride of lime, and the principle of their bleaching action is the same for all) are used in laundries by inexperienced hands, the carelessness-or rather the ignorance, more frequently-of the operator in using the bleaching agent generally results in the destruction of the material as well as the destruction of color; hence the horror with which all prudent housewives regard the use of "chemicals" in laundries. That this dislike is well warranted I can vouch from personal experience. I used to wear large white aprons to entirely cover my dress when I was doing much practical work in the laboratory. On the first occasion when I sent my aprons to the wash, I pointed out sundry stains to the laundress, saying that they would probably wash into holes, as they were caused by chemicals. Shortly afterwards, a table-cloth was returned full of small holes. Asked as to them, the laundress calmly replied: "Oh, yes; that is Miss Bradlaugh's chemicals"! Did she, I wondered, imagine that I was in the habit of assisting our appetites at breakfast or dinner by the concoction of some pleasant trifle like chlorine gas, or sulphuretted hydrogen? What, without doubt, did happen, is this: The cloth lay on the top of the things in the washing-tub, and the laundress, instead of making a dilute solution of her bleaching powder before putting it in the tub, had simply scattered the solid powder over the surface, and wherever it fell on the cloth there came a hole. So after all it was somebody's "chemicals", although not mine. Ozone is sometimes used as a bleaching agent, especially for the decolorizing of engravings discolored by age. Ozone is merely a concentrated form of oxygen with especially active properties; needless to say, therefore, that it bleaches by oxidation. The power of forming a colorless compound with hydrogen has been said to belong to all colored substances, and when this occurs it is called bleaching by reduction. The best known substance used in this manner is sulphur dioxide (SO2). Sulphur dioxide bleaches organic (principally vegetable) color-matters in the presence of moisture. It is supposed by some chemists that the sulphur dioxide takes up all the oxygen and part of the hydrogen from the moisture, leaving some free hydrogen, which, in its nascent (ie., just liberated) condition, has the power to unite with the color-matter to form a colorless compound. Sulphur dioxide is largely used in the decolorization of silks, wool, isinglass, sponge, and other articles which would be injured by chlorine. Articles to be bleached in this manner are usually moistened and then suspended over burning sulphur; the sulphur in burning is transformed into sulphur dioxide. The great drawback to its use is that if any oxidizing agent is brought into contact, the oxygen soon withdraws the hydrogen from the white compound which has resulted from its combination with some color-matter, and the color therefore reappears. For instance, fruit stains bleached by sulphur dioxide soon regain their color on exposing their cloth to the air; the color may be restored to a bleached red rose by washing the flower in sulphuric acid (oil of vitriol). An alkali will also neutralise the effect of the sulphur dioxide; this may be seen every day in the washing of new flannel with ordinary soap, when it will be found that the yellow color is reproduced. A favorite substance for removing ink stains or ironmould is salt of lemons, or salt of sorrel. It is an oxalate of potash, and can be artificially prepared, although it is found naturally in various kinds of sorrel. It removes ink or (other) iron stains by combining with the oxide of iron present in them to form a soluble salt, which soon disappears in washing. The salt of lemons should, however, be used with great care, as it is very poisonous. HYPATIA BRADLAUGH BONNER. (To be continued.) The Irrational Knot. BY GEORGE BERNARD SHAW, AUTHOR OF "AN UNSOCIAL SOCIALIST", ETC. CHAPTER IX.-(Continued.) THEN he began, seriously, "Is it too soon to call you by your own name? Miss Lind' is distant; but Marian' might shock you if it came too confidently without preparation." "Whichever you please." "Whichever I please!" "That is the worst of being a woman. Little speeches that are sheer coquetry when you analyse them, come to our lips and escape even when we are most anxious to be straightforward." "In the same way," said Conolly, "the most enlightened men often express themselves in a purely conventional manner on subjects on which they have the deepest convictions." This sententious utterance had the effect of extinguishing the conversation for some moments, Marian being unable to think of a worthy rejoinder. At last she said, "What is your name?" "Edward, or, familiarly, Ned. Commonly Ted. In America, Ed. With, of course, the diminutives Neddy, Teddy, and Eddy." "I think I should prefer Ned." "I prefer Ned myself." "Have you any other name?" "Yes; but it is a secret. Why people should be plagued with two Christian names, I do not know. No one would have believed in the motor if they had known that my name was Sebastian." "Sebastian!" "Hush. I was actually christened Edoardo Sebastiano Conolly. My father used to spell his name Conolly whilst he was out of Italy. I have frustrated the bounty of my godfathers by suppressing all but the sensible Edward Conolly." There was a pause. Then Marian spoke. "Do you intend to make our-our engagement known at once ? "I have considered the point; and as you are the person likely to be inconvenienced by its publication, I am bound to let you conceal it for the present, if you wish to. It must transpire sometime: the sooner the better. You will feel uncomfortably deceitful with such a secret in your possession; for, if your friends make plans for youfriends always do-they will force you to play the hypocrite. As for me, every time your father greets me cordially in the City I shall feel like Iago. However, you can watch for your opportunity. Let me know at once when the revelation takes place." "I will. I think, as you say, the right course is to tell at once." "Undoubtedly. But from the moment you do so until we are married you will be worried by remonstrances, entreaties, threats, and what not; so that we cannot possibly make that interval too short." Marian looked thoughtful, and did not answer. "I do not wish to hurry you; but when I have once resolved to take any step, I am impatient of delay." "I am only impatient when I am about to do something involving a risk," said Marian gravely, looking inquiringly at him. "I am just the reverse, ," he replied quickly. "I am never in a hurry to run a risk. But I am not fond of postponing an accession to my happiness." "That is what I am anxious about. You must not be so confident that I will bring you happiness. I am afraid that you have been thinking so much of the unreal reasons for my not marrying you, that you have forgotten many real reasons why you should seek further and fare better in your choice of a wife." "Dont begin to calculate in that way, or you will awake to the sacrifices you have to make in marrying at all, and perhaps rescind. Which is an additional reason, by the bye, why I should be in haste to wed." "Pray be serious-if only to give me confidence," said Marian, uneasily. "You have thought so profoundly on other subjects, that I am depending on you for having thought out that of our marriage too." "I cannot accept the responsibility," he said. "It might make it my duty to dissuade you. Profound thought is nonsense: the maximum depth of thought is about one inch. I have done with thought on the subject; and I will never be serious again touching it until I have experience to guide me. But it is growing late; and we have a few things to settle still. First, how we can contrive to meet one another. We must confer about business as well as personal matters. There is a house to be chosen, a date to be fixed, progress at home to be reported, and-if you please-my desire to see you often to be gratified." "We must take Nelly into our confidence. You will not object to that?" "Certainly not. I like Miss McQuench." "You really do! Oh, I am so glad. Well, we are accustomed to go about together, especially to picture galleries. We can come to the Academy as often as we like; and you can come as often as you like, can you not?" "Tomorrow, for instance." "Yes, if you wish." "Let us say between half-past four and five, then. I would willingly be here when the doors open in the morning; but my business will not do itself whilst I am philandering and making you tired of me before your time. The consciousness of having done a day's work is necessary to my complete happiness." "I, too, have my day's work to do, silly as it is. I have to housekeep; to receive visitors; to write notes about nothing; and to think of the future. We can say half-past four or any later hour that may suit you." "Agreed. And now, Marian "Dont let me disturb you," said Miss McQuench, at his elbow, to Marian; "but Mrs. Leith Fairfax will be in here with Sholto Douglas presently; and I thought you might like to have an opportunity of avoiding him. How do you do, Mr. Conolly?" "I must see him sooner or later," said Marian rising. "Better face him at once and get it over. I will go back by myself and meet them." Then, with a smile at Conolly, she went out through the door leading to the gallery of pictures in water color. "Marian does not stand on much ceremony with you, Mr. Conolly," said Miss McQuench, glancing at him. "No," said Conolly gravely. Academy?" "What do you think of the "I never think about it now. I look at the show and am thankful. |