LECTURES AND ESSAYS READ AT INSTITUTES 203 



ever, but you can easily do so by dropping a lump of parafline in the centre 

 of eacli tumbler immediately after you have filled it, and while it is still hot 

 enough to melt the paraffine and form a continuous film on tlio top. This 

 exceedingly cleanly and useful substance is easily applied, and will exclude the 

 air perfectly. 



"Sometimes I don'"c have any luck with my jelly, and it won't set, or rather 

 get hard." That is because the fruit you used was too ripe. Tiie juice of 

 fruits just ripening contains a pecuHar substance called pectose, which bv 

 being heated for a time will solidify upon cooling. As the fruit continues to 

 ripen this pectose is converted into pectin, which has not this valuable prop- 

 erty of becoming jelly. It is necessary, therefore, to insure success m jelly 

 making, that the fruit be not dead ripe, on the contrary it should just be 

 approaching ripeness. If the expressed juice is left in contact with the mass 

 from which it was expressed it absorbs more pectose from the tissue compos- 

 ing the mass and is tlien more easily made into jelly. As we pass out of the 

 pantry I notice the sugar barrel standing in one corner, there is instantly 

 brought to mind the bane of modern existence — glucose again. 



" How can we tell whether our best granulated sugar contains glucose?" 

 I should say that you could not unless you have a mind to experiment and 

 really become an analytical chemist in a small way. Fehling's test by the 

 reduction and precipitation of copper is the old fashioned Way, and the use of 

 polarized light in asaccharometer costing about $100, is the new way; but here 

 is a simple little test that is so easdy applied that it will be found quite useful 

 (Picrate Potash). Aside from tliis test large adulteration can be told by the 

 tendency of the sugar to lump in the bowl. 



As it is getting late let us adjourn to the back yard and look at the leach 

 and soap kettle. Among the many joyous signs of spring and the return of 

 the budding flowers and glad voices of birds, the smell of soap boiling holds a 

 front rank. But why do we go to all this fuss to make soap? Why isn't the 

 lye as it comes from the leach just what we want — what is the use of saving 

 old grease, aged butter, poor tallow, to mix with lye to make a substance to 

 be used in removing this same grease from dishes, clothes, woodwork, tables, 

 etc. That is the natural inquiry but if you should use the lye you would find 

 of course that it was too strong. It removes grease; certainly, but it also 

 takes the skin off the hands of those using it. It takes dirt off the woodwork; 

 yes, and the paint too. It removes the dirt from soiled clothes; yes, and 

 destroys the fabric of the cloth more than a year's wear would do. This over 

 zealous disposition of the free alkali in lye from leached ashes is overcome and 

 made more conducive to our convenience by uniting it with an acid and con- 

 verting into a very slightly alkaline or nearly neutral salt — and this salt or 

 chemical combination is soap. 



If we consider the substance known as tallow to be a chemical combination 

 of the stearate, margarate, and oleate of glycerol, we will perhaps be able to 

 understand the changes which occur when lye is boiled up with soap grease. 

 Agreeable to the law of chemical attraction the stronger bases of the lye, 

 that is, the potasli and soda, replace the weaker base glycerol, and we will 

 have formed the stearate, margarate and oleate of potash and soda, which is 

 soap, and the oxide of glycerol or glycerine, as we call it, will be formed. 



This soap, after it is thoroughly well made, retains its strength indefinitely. 

 Exposure to the air does not measurably Avcaken the strength of tlie alkali, as 

 would bo the case were it uncombined ; and, besides the merit of stability, it 

 has the great one of portability. When this stearate, margarate, and oleate 



