WATER ANALYSIS 29 



o-oi mgr. Fe ; (2) Dilute HNO 3 solution : make up 

 30 c.c. of pure concentrated acid to 100 ex. with distilled 

 water ; (3) Potassium sulphocyanate solution : 15 grm. 

 KCNS dissolved in 100 c.c. of distilled water. 



Process. To each of two Nessler glasses add 5 c.c. of 

 each solution (2) and (3). Add 1 c.c. of standard solution 

 to one, and to the other add a measured quantity of 

 sample, say 10 c.c, and note depth of tint produced, 

 compared to standard. If the two are near each other, 

 proceed jas before to match. If the sample is much too 

 dark, use less ; if much too light, use more. Always make 

 up bulk in each Nessler to be approximately equal to each 

 other by adding distilled water, before finally matching. 

 If more than 3 c.c. of standard solution are required, the 

 tint gets too deep. 



Iron is perceptible to taste when present to the extent 

 of I gr. per gallon, or 1 part in 350,000 parts of water. 



Zinc is usually determined gravimetrically. It may be 

 done volumetrically with standard solution of potassium 

 ferrocyanide, using copper sulphate as an indicator, the 

 brown copper precipitate not being formed until all the Zn 

 is precipitated. The standard solution is made 0-324 grm. 

 of K 4 Fe(CN) 6 . 3H 2 per litre. Then 1 c.c. = o-i mgr. Zn. 



Lime and Magnesia. These are often present together 

 from strata. 



Lime. Ammonium oxalate gives a turbidity with 9 

 parts per 100,000, and a white precipitate with anything 

 over 20 parts per 100,000. 



Magnesia. Precipitate any lime present with ammonium 

 oxalate, filter, then add AmCl, AmOH, and sodium phos- 

 phate. Crystals of so-called triple phosphate will separate 

 out in twenty-four hours. (MgNH 4 P0 4 .) 



For this and the next test it is better to concentrate 

 to V 



Phosphates. Add some dilute nitric acid, stir, add 

 excess of ammonium molybdate, and heat. If phosphates 

 are present, a yellow colour will form. 



Sulphates. Add dilute HC1 and barium chloride 

 solution a white precipitate of sulphate of barium,, 

 insoluble in all acids. 



