PROCEEDINGS OP SECTION B. 337 



and filter through a dry filter, rejecting the first portion of filtrate ; draw 

 off 100c. c. of filtrate ( =: 70c. c. of original water) and titrate with 

 N/i oHCl and methyl orange. This method, although apparently quicker 

 than the way chosen, in practice occupies much more time and attention. 

 It is, however, somewhat more accurate, since if in determination 2 the 

 ppt. is not washed free of NaoCOg, low results will be obtained, and if 

 it is washed too much a sufficient amount of the precipitated carbonates 

 will be dissolved to vitiate the results. If three and not more washings 

 are made in following out determination 2, the results are practically cor- 

 rect. On account of the quicker and simpler work required, this way 

 has been given the preference. 



{b) The other modification is to use a mixture containing equal 

 volumes of N/, oNaOH and N/i oNaaCOs (" soda reagent ") in place of 

 the N/'ioNaaCOg. So far as our expei'ience goes there is no practical 

 advantage in this, provided a considerable excess of N/mNaaCOa is used in 

 determination 2. This has been confirmed by Gardner & Lloyd (J.S.C.I., 

 April, 19U5). 



If only a slight excess is used the MgCOs is not fully precipitated, and 

 erroneous results are obtained. The " soda reagent " has apparently the 

 advantage that it represents more nearly the action which will take place 

 in the actual softening treatment of the water, but this in practice does 

 not render the determination any more accurate. Careful tests made 

 with both yielded agreeing results, so that either reagent may be used in 

 determining the permanent hardness. Jena, or resistance glass vessels, 

 should be used in this determination to reduce the action on the soda, 

 and this is especially necessary in the case of the mixed " soda reagent " 

 being used. 



The method of analysis here outlined possesses many advantages over 

 the older methods, in that a water can be tested with less labor, in less 

 time, and at less cost of materials : and further than this — more practical 

 information as to the character of the water is obtained than by the 

 more usual method of determining the bases and acids independently 

 and calculating the salts. The method is therefore worthy of attention 

 by those who are called upon to make technical examinations of boiler 

 waters. 



