upon Water containing a Salt of Magnesia, 175 



seen that onlv as far as the 6th degree do the magnesia cor- 

 respond, or nearly so, with the lime standards. And as the 

 strength of the solutions increase, so much more do the dif- 

 ferences increase, until a standard of 16° magnesia, and a 

 standard of 9° lime, require nearly the same number of soap- 

 test measures lo produce a proper lather in each. 



Some experience is requisite in making experiments upon 

 water containing magnesian salts alone, and likewise upon 

 magnesian water mixed with lime salts. Magnesian salts in 

 water more or less produce a curd with soap which interferes 

 in some measure with the lather. They likewise do not act 

 so readily upon soap as the salts of lime do ; so that in making 

 an experiment, a good deal more agitation is required to pro- 

 duce a lather. I have found it best to add the soap-test little 

 by little with agitation ; in fact, all solutions should be treated 

 in the same manner as when a water of unknown hardness 

 has to be tested. If the requisite quantity of soap-test be 

 added at once to a standard, a good deal of shaking is required 

 to produce even a curd: this is more the case as the quantity 

 of magnesia increases, but by additional shaking the lather 

 appears. A proper lather once having been obtained, it 

 can with very moderate shaking be restored again, not only 

 for hours but for days afterwards, and improved as to sta- 

 bility. The addition however of a little more soap-test with 

 gentle agitation, instead of at once improving the lather, has 

 the contrary effect, and a curd appears instead of the lather, 

 or apparently the water is rendered hard, and it is only by 

 very considerable agitation that the lather can be restored ; 

 when restored, it is a better lather than before the addition of 

 the last portion of soap-test : this operation may be repeated 

 upon the same solution several times and with similar re- 

 sults, by proceeding as above described, until a considerable 

 amount of soap-test measures have been added above the 

 quantity requisite to produce a proper lather. This is more 

 particularly the case in the higher degrees. 



Table No. 2. 16° Lime plus Magnesia degrees. — On re- 

 ferring to this table, it will be seen that the solution of 16° 



» 



lime plus ]° magnesia, actually does not require so much 

 soap-test to form a perfect lather as does the solution of 16° 

 of lime alone, and as the magnesia increases in the solutions, 

 the soap-test measures requisite to produce a lather diminish, 

 until the solution of 16° lime plus 16° magnesia gives a lather 

 with 27*9 measures, i. e. 4*1 soap-test measures less than is re- 

 quired by the standard of lime of 16° hardness. The action 

 of a few more soap-test measures, when added to solutions in 

 which a perfect lather had once been established, of appa- 



