of water; pour this into the iodide solution, shaking the latter, until a permanent red precipitate forms, add 600 c.c. of a 20 per cent solution of sodium hydroxide and then add more of the mercuric chloride solution until a permanent precipitate is produced. Allow the solution to stand for several days, and decant the clear solution for use. The reagent must be kept in a corked bottle. It improves on keeping. To prepare the standard ammonium chloride, dissolve 1.5683 grams of pure ammonium chloride and make up the volume to 500 c.c. with ammonia-free water. Take 10 c.c. of this solution and dilute to 1,000 c.c. This is the standard ammonia solution, of which 1 c.c. equals 0.00001 gram of ammonia (NH3).

Free Ammonia. Pour into a Nessler comparison tube 50 c.c. of the water, and into another tube 50 c.c. of ammonia-free water, with the addition of 0.1 c.c. of the standard ammonia solution. Then add to each tube 2 c.c. of Nessler reagent, and stir them well. If, after standing for a few minutes, the colors are about the same, take 500 c.c. of the water for the determination, and if the sample shows a much darker or lighter color than the standard, take a proportionately greater or less amount for the determination.

Pour into the retort a solution of 1 gram of sodium carbonate in 250 c.c. of water, and distil until the solution is free from ammonia. This is ascertained by testing portions of the distillate with the Nessler reagent. Cool the solution in the retort, and introduce the requisite amount of the water to be examined. Again start the distillation, catching the distillate in 50-c.c. Nessler tubes. To the tube containing the first 50 c.c. add 2 c.c. of the Nessler reagent; stir it well, and place the tube on a white tile. Take 0.4 c.c. of the standard ammonium chloride solution, dilute to the mark in another tube, mix in the Nessler reagent and, after the two solutions have stood for a few minutes, compare the colors. If the standard is darker, pour out 25 c.c., dilute again to 50 c.c. and compare. If necessary, repeat this operation until the colors agree. If the standard is lighter than the sample, discard it, and try the comparison with a larger portion. Compare the second and third 50-c.c. portions of the distillate in the same way, continuing the distillation until a portion is obtained that is free from ammonia. The ammonia in the combined distillate is equal to

that contained in the total amount of the standard for the different portions.

Albuminoid Ammonia.-Prepare an alkaline potassium permanganate solution by dissolving 10 grams of potassium hydroxide and 0.5 gram of potassium permanganate in 50 c.c. of water. Boil the solution down to 25 c.c., and dilute to the original volume with ammonia-free water.

Cool the residue of water in the retort; add the alkaline permanganate solution, and make up the volume of the liquid to about 500 c.c. with ammonia-free water. Carry out the distillation and comparisons as in the determination of free ammonia.

DETERMINATION OF NITRITE

The reagents required are sulfanilic acid solution, made by dissolving 1 gram of sulfanilic acid with 300 c.c. of acetic acid (1:4); amidonaphthalene acetate, prepared by boiling 0.2 gram of alpha-naphthylamine with strong acetic acid, filtering and diluting to 400 c.c. with dilute acetic acid, and standard sodium nitrite solution, prepared by dissolving 0.1098 gram of silver nitrite in 100 c.c. of water, adding to this a slight excess of sodium chloride and making up the volume to 1,000 c.c. One cubic centimeter of this solution will contain 0.00001 gram of nitrogen as nitrite.

Take 25 c.c. of the water in a Nessler tube, and mix it with 2 c.c. each of sulfanilic acid and amidonaphthalene acetate solutions. Transfer to another tube 25 c.c. of distilled water and 0.2 c.c. of standard nitrite solution; stir in the reagents, and after allowing the solutions in both tubes to stand a few minutes, compare the colors. Change the standard by diluting it or by adding more of the sodium nitrite until the colors agree. Repeat the test, using the amount of standard nitrite required in the preliminary test, and repeat the operation with the use of more or less of the standard until the colors agree when the two solutions are treated at the same time. Simultaneous treatment of

the two is essential.

DETERMINATION OF NITRATE

Prepare a solution of phenyl-hydrogen sulfate by thoroughly mixing 6 grams of pure phenol with 3 c.c. of water and 37 c.c. of

strong sulfuric acid. Prepare a standard potassium nitrate solution by heating potassium nitrate in a crucible just to the fusion point, dissolving exactly 0.722 gram of this in water and making up the volume of the solution to a liter. One cubic centimeter contains 0.0001 gram of nitrogen as nitrate.

Take 25 c.c. of the water in a small porcelain dish, transfer to another dish 1 c.c. of the standard nitrate solution and 24 c.c. of pure water, evaporate both solutions to dryness on the waterbath, add to each dish 1 c.c. of the phenyl-hydrogen sulfate solution and mix with small glass rods. When the dishes are cold add to each 1 c.c. of distilled water, then add 3 drops of strong sulfuric acid, mix, then remove the rods, rinsing them with distilled water. Heat the solutions on the water-bath for a few minutes, add to each 25 c.c. of pure water, make ammoniacal and transfer to 250-c.c. graduated cylinders with glass stoppers. Dilute the solutions to 100 c.c., pour the one showing the lightest color into a Nessler tube and dilute the other with water until, after mixing and pouring out 100 c.c. into another Nessler tube, the colors agree. The nitrogen as nitrate is found as follows: Nitrogen per 1,000 c.c. =

0.004 X number c.c. of sample after diluting number of c.c. of standard after diluting

LIME AND SODA ASH REQUIRED FOR SOFTENING

To determine the amount of lime and soda ash to add to soften the water, proceed as follows:

Put in a 250-c.c. Jena flask 200 c.c. of the water to be tested, add 50 c.c. of saturated lime water and heat to boiling. Cool, shake well and filter through a rapid filter, wash three times with pure, freshly boiled water, and titrate the filtrate with 0.0357N HCl, using methyl orange as indicator. Treat 200 c.c. of freshly boiled distilled water in exactly the same way, being careful to use the same amount of methyl orange in both cases and to finish at the same depth of color. The number of cubic centimeters of standard HCl used the second time, minus the number of cubic centimeters used the first time, multiplied by 5 gives the parts of lime to add to a million parts of water.

Now add to the titrated water in a porcelain dish 30 c.c. of 0.0714N Na2CO3, heat to boiling, cool, filter and titrate the excess

of soda. The sodium carbonate precipitates both the CaCl2 made in the first titration and the CaSO4, etc., in the water. Therefore, to calculate the amount of sodium carbonate necessary to soften the water, subtract from 2X30-60, the total amount of 0.0357N HCl that has been used in both titrations and multiply by 9.45.

Methyl Orange Solution.-Dissolve 0.025 gram of the sodium salt in 100 c.c. of water and add 0.7 c.c. of 0.10N HCI.

REFERENCES:

DRAWE, Z. angew. Chem., 23, 52.

PROCTOR, J. Soc. Chem. Ind. (Jan. 15, 1904).

American Public Health Association, Standard Methods for Water
Analysis.

WYSOR, "Analysis of Metallurgical and Engineering Materials." Calculation of the Results. In stating the results of the analysis it is customary to combine the acids and the bases in the following manner: The alkalies are first combined with the chlorine, any excess being then combined with the sulfuric acid. Should there be more chlorine than will combine with the alkalies, the excess is calculated first to the calcium and when that is used up, to the magnesium. Should there be alkalies more than sufficient to saturate both the chlorine and the sulfuric acid, the excess is estimated as carbonate.

The sulfuric acid left after the alkalies are satisfied is then united with the calcium and any excess combined with the magnesium.

All the calcium and magnesium not required for the chlorine and the sulfuric acid are then calculated as carbonates.

This order can be departed from where there is reason for some other combination. In water that has been treated with lime and soda to remove the lime, magnesia is frequently present as hydroxide. In estimating the effect of the magnesia compounds in causing corrosion in boilers, all the chlorine and the sulfuric acid in excess of that required to saturate the alkalies should be considered as combined with the magnesia. The table at the end of the book will be found useful in making these calculations.

The analysis should be reported in parts per million and in grains per gallon. To convert parts per million to grains per gallon multiply by 0.058353.

Instead of reporting as above it is often preferred to report as the ions or as the oxides without making assumptions as to the combinations of the oxides or un-ionized molecules.

CHAPTER XLVI

CALCULATION OF NORMAL SOLUTIONS

A normal solution, as used in this book, is a solution a liter of which contains 1 gram atomic weight of active hydrogen or its equivalent. Thus a normal solution of HCl will contain 1.008 grams of hydrogen, or 36.468 grams of HCl in a liter, a liter of normal H2SO4 will contain 1.008 grams of hydrogen, or 49.043 grams of H2SO4. A liter of normal NaOH contains 1.008 grams of hydrogen, or 40.008 grams of NaOH, and a liter of normal NH4OH contains 1.008 grams of hydroxyl hydrogen, or 35.05 grams of NH4OH. If an acid such as H3PO4 is used in a reaction wherein only two of its hydrogen atoms are active acid ions, a normal solution will contain one-half of the gram molecular weight of phosphoric acid in a liter, while if in the reaction all three of the hydrogen atoms are active, a liter of normal phosphoric acid solution will contain one-third of the gram atomic weight of phosphoric acid. That is, the amount of an acid or alkali contained in a liter of a normal solution depends upon the reaction for which the reagent is to be used, but it will always contain 1 gram atomic weight of hydrogen which will take part in the given reaction.

With oxidizing and reducing solutions the same principle holds good. For instance, 1 gram molecular weight of KMnO, in an acid solution will give up oxygen sufficient to oxidize 5.04 grams of hydrogen; therefore, a normal solution of permanganate when it is to be used in an acid solution will contain one-fifth of the gram molecular weight of KMnO4 per liter. In an alkaline solution, 1 gram molecular weight of KMnO4 will only oxidize the equivalent of 3.024 grams of hydrogen; therefore, when it is to be used in an alkaline solution (as in the Volhard method for manganese) a liter of normal solution will contain one-third of the gram molecular weight of KMnO4.

In making up normal solutions (or fractional normal solutions) of oxidizing or reducing reagents it is most convenient to consider the change in valence which the reagent undergoes. Thus, when