Litmus solution

Lackmus, m., -farbstoff, m. litmus, -fiechte,/. litmus lichen, archil, -losung, /. litmus solution. -papier, n. litmus paper. 

To the practical chemist, the utility of litmus arises from the way its colour changes as a function of pH. Placing a single drop of litmus solution into a beaker of solution allows us an instant test of the acidity (or lack of it). It indicates whether the pH is less than 7 (the litmus is red, so the solution is acidic), or the pH is greater than 7 (the litmus is blue, so the solution is alkaline). Accordingly, we call litmus a pH indicator. 

Electrolysis of Sodium Sulphate Solution. Use the device of the preceding experiment. Pour a 5% sodium sulphate solution into the U-tube and add two drops of a neutral litmus solution to each arm of the tube. Switch on the current (it should be about 2 A). Observe the phenomena occurring at the electrodes. Write the equations of the corresponding reactions. What is known as the electrolyte decomposition voltage ... 

The experiment is prepared by one student and demonstrated to the class. Assemble a device for electrolysis (see Fig. 52). Include rheostat 1 for 10-20 Q and ammeter 2 for 2-3 A in the circuit. Pour a saturated sodium chloride solution coloured with a neutral litmus solution into U-tube 3. Immerse carbon electrodes 4 (by one-third) into the solution. Connect the ends of the conductors to a direct-current source (an accumulator) and pass a current of about 2 A through the solution. What is observed Explain the change in the colour of the indicator solution. Write the equations of the reactions proceeding at the electrodes. 

Preparation of Nitric Acid by Oxidizing Ammonia. Assemble an apparatus as shown in Fig. 90. Pour a 2% ammonia solution into flask 1. Put a loose layer of freshly roasted platinized asbestos into the middle of tube 2 over a length of 4-5 cm. Pour a neutral litmus solution or several drops of methyl red into flask 3 and connect the short tube of this flask to water-jet pump 4. Heat the platinized asbestos slightly with the flame of a gas burner and pass through it... 

In discussing an experiment by Priestley—in which an electric spark passed through air confined over litmus solution in an inverted U-tube produced an acid reaction on the litmus (oxidation of nitrogen to nitrous acid)—Bergman makes this interesting statement ... 

Litmus is a purple dye extracted from lichens and sea weeds. Lichens grow abundantly along the Mediterranean coast. Litmus readily dissolves in water to form a purple solution. This solution is used as an indicator to find out whether a solution is acidic or alkaline. Acid turns the litmus solution red and the base turns the litmus solution blue. 

Litmus paper is made by dipping absorbent paper in the litmus solution, drying it and cutting it into strips. Generally, litmus paper is used as an indicator as it is easy to use. ... 

Run 10 cc. of 1N hydrochloric acid into a beaker, add 1 drop of litmus solution, and then add IN sodium hydroxide until the color changes to blue. Add a drop or two more acid until the color again changes, and finally bring the solution to the exact neutral point when 1 drop of acid will turn the litmus red and a single drop of base will bring back the blue. 

Hydrolysis of Ammonium Salts. Boil for some time a solution of ammonium sulphate to which has been added a few drops of blue litmus solution. Pass the vapors into a flask of water containing a few drops of red litmus. The litmus in the boiling flask slowly turns red. The litmus in the flask in which the vapors are condensed turns blue. 

Ferrous sulphate, 2-normal III, XI Lead acetate, 1-normal IV Litmus solution, blue III Litmus solution, red III Magnesium chloride, 1-normal P. 55, V... 

The blue dye lacca, which can be extracted from the lichens Roccella and Leca-nora with alkali and milk of lime, is the basis for the well-known litmus solution, which functions as an acid-base indicator in the pH range 4.4-8.0. The name litmus comes from the Dutch lackmoes (from moes = mush, paste). 

The litmus solution, which is violet in neutral solution, turns blue in the presence of bases and red when acids are added. The main component of litmus is a polymer containing 7-hydroxy-2-phenazinone chromophores. Other natu-... 

The above discussion is valid only if the papers are prepared from solutions of pure indicators. This condition is not fulfilled by blue and red litmus paper. Blue litmus paper contains an exc ess of base and red litmus paper an excess of acid. Thus it is easy to see that, up to a certain concentration of the indicator, litmus paper will be more sensitive towards or OH the more dilute is the original litmus solution from which it is prepared. To a lesser degree, this is true also of violet litmus paper because it always contains small quantities of ampholytes. 

Litmus 4417-18 A dyestuff obtained from certain lichens. Paoer soaked in litmus solution is used to test scidity/alkellnlty ... 

If the flask be filled with hydrochloric acid gas and the water in the dish be the ordinary (diluted) blue litmus solution the fountain wUl change from blue to red. 

Red litmus solution as used above is made by adding a drop or two of acid to the ordinary blue solution. In neither case should the colour be too deep. 

Bright yellow crystals. Very faint acrid odor. Stable in air, but is dec by sunlight, mp 105-107. Insol in water. One gram dissolves in about 60 ml alcohol, in 10 ml benzene, in 50 ml vegetable oils moderately sol in chloroform and in carbon tetrachloride. The alcoholic soln is neurr L to litmus. Solutions may be heated to 120 without dec. Destroyed by alkalies and reducing agents. Keep protected from light. LD, orally in mice approx 0.5 g/kg, Molitor, Robinson, Proc. Soc. Exp. Biol. Med. 43, 725 (1940). 

P -h 5 02= = >2P20s When water is poured into the jar the oxide dissolves and phosphoric acid is formed, which changes the colour of blue litmus solution to red ... 

Some of Priestley s best later work was on the oxides of nitrogen and nitric acid. He found that when electric sparks are passed through air confined over litmus solution an acid is formed and the air contracts when the experiment was performed over lime water a precipitate was formed, hence he concluded, incorrectly, that the acid is fixed air (carbonic acid). This must have been formed from dust, etc., in the apparatus. In these experiments he used a straight sparking tube (i6), Fig. 24, but in order to be sure that the metal wire was not contributing to the effect he repeated them in a bent tube (19) with each leg in a cup of mercury, an apparatus later used by Cavendish (see p. 339), who showed that the acid is not fixed air but nitrous and nitric acids. 

Litmus solution in the tube became red, and the air was diminished on sparking, conformably to what was observed by Dr. Priestley , but with lime water no cloudiness was observed, although the air was diminished by one-third, and hence no fixed air was produced. With oxygen in the tube there was only a very slight diminution and the litmus was bleached (probably owing to the formation of ozone). After sparking over litmus, fixed air was formed, as shown by the lime water test. With soap-lees (caustic potash solution) in the tube the absorption in the case of air was more rapid than with water. 

The wjilei in the oiii inal jui may )c slightly alkaline tlien for the rcmethyl orange for blue, litmus solution for green, chlorophyll for violet, a dye. I hit only just sufficient of each for the desired effect in the bottom of the respective glasses. 

Chemicals.—Methyl orange, litmus solution, chlorine water or tincture of iodine, sulphate of indigo, caustic soda. 

Iron percfiloride and potassium sulphocyanide give a blood-red, decolourized by mercuric chloride potassium sulphocyanide and sulphuric acid a fine old port colour, cleared by the same agent Litmus solution and an acid produce red, also permanganate of potash and sulphuric acid, cleared by hyposulphite of soda. Potassium ferrocyanide and the double sulphate of uranium and potassium give an old port-like colour-washing soda clears it. 

Iijdrocliloric acid, and the solution in the beaker is ordinary blue litmus solution, diluted with water to the colour desired. The acid reaction clianges the blue fountain to a red one. 

Litmus solution is purple. Litmus Adds turns litmus solution red. 

Alkalis turn litmus solution blue, and red litmus paper blue. 

Many substances do not affect the colour of litmus solution so they are not acids or alkalis. They are neutral. Sodium chloride and sugar solutions are both neutral. 

What effect do alkalis have on litmus solution ... 

What colour would litmus solution turn, if you mixed it with Ajax Why ... 

What colour change would you see, on adding litmus solution to a solution of phosphorus pentoxide ... 

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