334 PROCEEDINGS OF SECTION B. 



ammonia, and boil ; then add boiling solution of ammonium oxalate ; 

 filter; wash with boiling distilled water till free from oxalates; prick the 

 filter; dissolve the ppt. with hot dilute HaSO^ ; boil solution, and titrate 

 hot with KMnO^N/^^, sol. 



Let C be number of c.c.'s required. 

 Then Hca =: C. 

 And hardness due to magnesium = Hmg = H — Hca. 



4. Chlorine. — Determine in the usual way — by titrating 70c.c. of 

 sample with standard AgNOg (4"7888 grammes per litre) and K„Cr207. 



Let S =: number of c.c.'s required. 



S X 1-408 = CI in terms CaCOoper gallon. 



5. Sulphates. — Determine as usual, by precipitation with BaCL, 

 using 350c. c. of sample. 



Mgms of BaSO^ from 70c. c. of sample X 0"4285 = SO^ in terms of 

 CaCOg per gallon. 



6. Total Solids. — Evaporate 70c. c. in platinum dish on asbestos jiad 

 over low flame burner to dryness ; bake in air oven i50°C. 



This is the whole of the laboratory work required for the calculation 

 of the assumed composition of the total solids. For all practical pur- 

 poses only determinations 1 , 2, and 3 need be made, and from these 

 three alone suitable treatment can be calculated tlius : — 



I. Using CaO and NasCOg — 



1. 0-5ii X (Ht -H Hmg) = lbs. of real CaO required per 7,000 



gallons of sample. 



2. 1-06 X Hp — lbs. of real dry NaoCO.-s required per 7,000 



gallons of sample. 



II. UsingNaOHandNa,CO.,— 



l. 0-8 X (Ht + Hmg) = lbs. of NaOH required per 7,000 



gallons of sample. 

 2. 1-06 X [Hp - (Ht + Hmg)] = lbs. of dry NaoCOg re- 

 quired per 7,000 gallons of sample. 

 The treated water can be quickly examined by determinations 1, 2, 

 and 3, and the water treatment readily controlled. 



Calculation of Total Solids. — For purposes of report or comparison 

 with other analyses, it may be desirable to set out the composition of the 

 salts. For this, determinations of 4. 5, and G are required in addition to 

 the first three. Although the bases and acids are probably not combined 

 as salts in the Avater, still it is usual to calculate the composition of the 

 total solids upon some assumption as to the preference of certain basic ions 

 for certain acid ions. Two assumptions present themselves, namely — 

 either that the acid ions should be allotted to the basic ions in sequence 

 (as chlorine to sodium, potassium, magnesium, and calcium in succession, 

 then CO 3 and SO^ allotted in turn), or else the basic ions are distributed 

 to the acid ions in succession. For many reasons we adopt the latter, 

 and the results seem more in accord with those shown by the method of 

 analysis stated above. 



