rVJ WATERS 49 



BORIC ACID.— OFFICIAL. 

 (Glassware containing boron must not be used in this determination.) 



59 DETERMIN.\TIOX. 



Qualitative test. — Evaporate to dryness a part of the alkaline filtrate under 52, 

 treat with 1-2 cc. of water, and slightly acidify with dilute hydrochloric acid (1 to 1). 

 Add about 25 cc. of 95% alcohol, boil, filter, and repeat the extraction of the residue. 

 Make the filtrate slightly alkaline with sodium hydroxid solution and evaporate 

 to dryness. Add a little water, slightly acidify with dilute hydrochloric acid, and 

 place a strip of turmeric paper in the liquid. Evaporate to dryness on the steam 

 bath and continue the heating until the turmeric paper is dry. If boric acid is 

 present the turmeric paper takes on a cherry-red color. As a confirmatory test, 

 apply a drop of dilute ammonium hydroxid to the reddened paper, and a dark 

 olive color will be due to boric acid. 



Quantitative test. — It is not usually necessary to determine boric acid quantita- 

 tively. However, if it is necessary, the Gooch method^ is used. 



60 METHOD OF REPORTING RESULTS.— TENTATIVE. 



Report the bases and acids as positive and negative ions in milligrams per liter, 

 except in the case of silica, which report as such without considering how much is 

 present as the silicic acid ion and how much as free silica. Report iron and alumin- 

 ium together when present in unimportant quantities, and in calculations consider 

 it as iron. When iron and aluminium are present in larger quantities make the 

 separation and report each separately. 



In calculating the hypothetical combinations of acid and basic ions join sodium 

 to nitrous, nitric, metaboric and arsenic acids; potassium to iodin and bromin; 

 calcium to phosphoric acid. Assign the residual basic ions in the following order; 

 ammonium, lithium, pota.ssium, sodium, magnesium, calcium, strontium, manganese, 

 iron and aluminium — to the residual acid ions in the following order: Chlorin, 

 sulphuric acid ion, carbonic acid ion, and bicarbonic acid ion. In case the bicar- 

 bonic acid ion is not present in a sufficient quantity to join with all the calcium, 

 the residual calcium is joined to silica to form calcium silicate, and manganese, iron, 

 and aluminium are calculated to the oxids MusO^, Fe20j, and AI2O3, respectively. 



INDUSTRIAL WATER. 



61 SOLIDS IN SOLUTION.— OFFICIAL. 

 Determine as directed under 7. 



62 CHLORIN.— OFFICIAL, 

 Determine as directed under 19. 



63 COMBINED CARBONIC AND BICARBONIC ACIDS.-OFFICLAL. 

 Determine as directed under 39. 



64 NITRATES.-OFFICLAL. 

 Determine as directed under 15 or 17. 



65 SILICA.-OFFICLAL. 



Determine as directed under 40. Generally one evaporation with hydrochloric 

 acid for removal of silica is sufficient. 



