66 



Lattin: Introduction 



total akalinity (methyl orange). The sample may be 

 collected by any method since there is no great 

 danger of changing the alkalinity. Both end points 

 may be determined on the same sample by using 

 phenolphthalein first and continuing with methyl 

 orange after the first end point has been determined. 



1) Phenolphthalein alkalinity: add four drops of phe- 

 nolphthalein indicator to 50 or 100 ml. of the sample 

 in a white porcelain casserole or an Erlenmeyer flask 

 over a white surface. If the solution becomes colored, 

 hydroxide or normal carbonate is present. Add 0.02 N 

 sulfuric acid from a burette until the coloration dis- 

 appears. The phenolphthalein alkalinity in parts per 

 million of calcium carbonate is equal to the number 

 of milliliters of 0.02 N acid multiplied by 20 if 50 ml. 

 of sample was used, or by 10 if 100 ml. was used. 



2) Methyl orange alkalinity: add two drops of methyl 

 orange indicator to 50 or 100 ml. of the sample or 

 to the solution to which phenolphthalein has been 

 added, in a white porcelain casserole or an Erlen- 

 meyer flask over a white surface. If the solution 

 becomes yellow, hydroxide, normal carbonate, or 

 bicarbonate is present. Add 0.02 N sulfuric acid until 

 the faintest pink coloration appears, that is, until 

 the color of the solution is no longer pure yellow. 

 The methyl orange alkalinity in parts per million of 

 calcium carbonate is equal to the total number of 

 milliliters of 0.02 N sulfuric acid used multiplied by 

 20 if 50 ml. of sample was used, or by 10 if 100 ml. 

 was used. 



Hydrogen-ion concentration. — The pH, or hydrogen- 

 ion concentration, is a measure of the degree of 

 acidity or alkalinity of a solution. A pH from 1-7 

 is acid, 7 is neutral, 7-14 is alkaline. The pH of a 

 water sample is taken by adding a few drops of an 

 indicator to the water and comparing the color to a 

 standard color chart of pH values. One method is to 

 use 0.5 ml. of "Universal pH Indicator" in a 10 ml. 

 sample of water in a glass tube 16 mm. in diameter. 

 The color is checked against a Harleco color chart 

 and the pH read off. It is also possible to use indi- 

 cators of known pH range. Here the color is checked 

 for exact pH against a set of color tubes of known 

 pH color value. The following are indicators with 

 their pH ranges given: 



Indicator 



P H 



Color Change 



Bromphenol blue 



3.0-4.6 



yellow-blue 



Bromcresol green 



4.0-5.6 



yellow-blue 



Chlorphenol red 



5.2-6.8 



yellow-red 



Bromthymol blue 



6.0-7.6 



yellow-blue 



Phenol red 



6.8-8.4 



yellow-red 



Thymol blue 



8.0-9.6 

 MAPPING 



yellow-blue 



from which most of the lake or stream section can 

 be seen. Measure the straight line distance between 

 these points. Set up the plane table over one end ot 

 the base line with its surface level and one side 

 oriented on a north-south line. 



Mark a convenient point on the paper to represent 

 the point over which the paper is set and label this 

 point A. Using point A as a center, sight with an 

 alidade or rule to the other end of the base line and 

 draw a fine line toward point B. With the known 

 distance between points A and B, determine a suit- 

 able scale, preferably one listed below, and mark off 

 on the AB line the distance, according to scale, 

 between A and B. 



From point A, sight around the shore line from left 

 to right, bringing the alidade to bear on each major 

 point and draw a line from A toward each point. Label 

 these lines 1, 2, 3, and so on, in order, and record 

 to what conspicuous object on the shore line each 

 number refers. Complete the circuit of the body of 

 water in this manner and then move the plane table 

 to point B. Reorient the table at point B and check 

 by taking a backsight from point B to point A, making 

 sure that the line between A and B corresponds to 

 the edge of the alidade when point A is viewed from B. 



From point B sight around the shore as before to 

 the various objects which were viewed from point A, 

 draw a line toward each from point B and number each 

 line to correspond with the lines from point A. The 

 point at which the lines intersect, when extended, is 

 the location on the map of the points selected. 



If the lake or stream is small and the shore line 

 entirely visible from the two points, two stations 

 will be enough. If part of the area is not visible, it 

 will be necessary to proceed to some point already 

 located by the intersection of two lines and orient 

 the plane table to correspond, and then set up another 

 base line to map the area that was not visible from 

 the first two stations. 



After all the shore line points have been located 

 by intersections, the details of the shore line between 

 the points may be filled in by careful freehand 

 sketching. 



Determination of area. — To determine the area of 

 a mapped lake, lay over the completed map a semi- 

 transparent sheet of coordinate paper ruled to one 

 inch squares. Count the number of whole squares 

 within the limits of the lake and carefully estimate 

 the inner area of the squares cut by the shore line. 

 Add the two together and record as square inches of 

 lake area. The following table gives the number of 

 acres per square inch of map area for various scales. 



Acres per square inch of map area 



Scale (feet per inch) Acres (per square inch) 



50 0.057 



Choose two points, A and B, as widely separated as 

 is convenient, 100 to 300 yards, near the shore, and 



100 

 200 

 350 

 500 



.230 

 .92 

 2.81 

 5.74 



