upon Water containing a Salt of Magnesia. 177 



action more fully, and for the first time the standard of lime 

 with 1° magnesia requires more soap- test to form a lather 

 than does the standard of lime alone; still it does not amount 

 to what would be necessary for 5° lime. The soap-test mea- 

 sures required to produce perfect lathers with 4°, 5°, 6° and 

 7°, are greater than was required in the last series of expe- 

 riments upon these numbers with the 6° standard of lime. 

 The same peculiarities of the soap-test upon some of these so- 

 lutions were observed in this set of experiments as in the last. 

 Table No. 7. 2° Lime with Magnesia degrees. — On ex- 

 amining this table, it will be seen lhat the solutions of this 

 standard of lime with the first four magnesia degrees appear to 

 require nearly as many soap-test measures as if thev were en- 

 tirely lime standards. It will likewise be observed, on com- 

 paring Table 4 with this table, that 7°, 8°, 9° magnesia with &° 

 lime, do not take each so many soap-test measures as 7°, 8°, 9° 

 magnesia with 2° lime, to form proper lathers. Again, in Table 

 No. 5, it will be seen that each of the magnesia degrees from 6° 

 to 16°, with the standard of lime which is 6°, do not take so 

 many soap-test measures to form proper lathers, as do these 

 magnesian solutions with 2° hardness of lime. On referring 

 to Table 6, the same remark applies to these solutions as to 

 the last, that is, that 2° lime with each of the standards of 

 magnesia from 6° to 16° require more soap-test to produce 

 proper lathers than solutions of 4° lime with each of these 

 magnesian standards require. I would call attention again 

 to Table 7, to notice a rapid descent in soap-test mea- 

 sures between 10° and 11° magnesia; I have made many ex- 

 periments if possible to explain this, but without success. I 

 can only observe, that in certain stages of a series of expe- 

 riments of a standard of lime with magnesia, it requires much 

 care, attention and observation, to mark when the lather pre- 

 vails over the curd, and to obtain at this particular stage uni- 

 form lathers, more especially when the soap inclines to form 

 a curd in a solution, together with a lather, at the same time. 

 If these points are not attended to, and no perseverance em- 

 ployed in agitating the solutions, uniform results cannot be 

 expected. The other observations I have made on the pre- 

 ceding series of waters are applicable to these. The inferences 

 which I draw from the foregoing experiments are as follows : — 



1st. That water containing sulphate of magnesia alone acts 

 towards the soap-test in producing with it a perfect lather, 

 similarly or nearly so, as does water containing a lime salt 

 alone, but only when the equivalent of magnesia salt does not 

 exceed 6 grs. of carbonate of lime in a gallon of water. 



2nd. That the degrees of hardness of an ordinary water 

 Phil. Mag. S. 3. Vol. 37. No. 249. Sept. 1850. N 



