176 Mr. D. Campbell on the Action of the Soap-Test 



rently rendering them hard, was noticed in these as in the 

 former solutions. 



Table No. 3. 12° Lime plus Magnesia degrees, — It will be 

 observed in this table that the magnesia acts similarly? although 

 scarcely so powerful as in the last experiments ; but on the 

 whole, the action of magnesia thoughout this series of expe- 

 riments very much accords with its action in the former. 



Table No. 4. 8° Lime plus Magnesia degrees. — On referring 

 to this table, it will be seen that the magnesia acts upon the 

 lime standard much as in the last experiments. 



Table No. 5. 6° Lime plus Magnesia degrees. — On ex- 

 amining this table, we find now that the magnesia begins to 

 act differently towards the lime than it has hitherto done ; 

 the 6° lime plus 1° magnesia is now equal in soap-test mea- 

 sures to 6° lime, at least the difference (02) may be considered 

 within the limits of error of experiment; from 2° mag. up to 

 6° there is a gradual rise, but at 7° it begins to fall, and con- 

 tinues to do so throughout the remaining solutions. I may 

 remark that the lathers from 7° to 16° are not produced with 

 the soap-test given in table, except with considerable agitation, 

 and although thin, are perfectly free from curd and are re- 

 producible at any future time by agitation. When a perfect 

 lather has been produced by the minimum quantity of soap- 

 test, the addition of a small quantity more will reduce the 

 lather to a curd ; great agitation may produce the lather 

 again, and stronger than it was before the last addition of 

 soap-test: if beyond a certain amount of soap-test has been 

 added, a new action shows itself, which I have failed to notice 

 in any of the previous solutions, which is, that shaking cannot 

 restore the lather properly again until a certain amount of 

 soap-test has been added; the additional quantities of soap* 

 test I have had to add are in the table, and opposite the so- 

 lutions in which I noticed this peculiarity; how to account 

 for it I know not, and have not as yet had time to investigate 

 into it. I am unable to account for the wide difference in the 

 amount of additional soap-tests between the numbers 7° and 8° ; 

 as the other numbers seem to follow regularly, it may be owing 

 to another point in some of these solutions at which much 

 agitation and less soap-test would produce a lather, but which, 

 although I have made many experiments, I have not succeeded 

 in hitting upon. When to the lather established after the 

 additional soap-tests a small quantity of soap-test is added, 

 it renders it curdy, but shaking will re-establish the lather 

 again. 



Table No. 6. 4° Lime mth Magnesia degrees, — On looking 

 over this table, it will be noticed that the magnesia comes into 



