618. To Test Soap

618.     To Test Soap. The readiest way to find whether soap will injure the delicate skin of women or children is to test it with the tongue. Good soap, in which the caustic alkali is neutralized by thorough combination with the fat, will not have a sharp taste. The soap used in medicine, and the transparent soaps, are neutral and good. Many toilet soaps, and especially the imitation marbled castile soap, so abundant in the trade, contain too much free alkali. They have not been thoroughly boiled, and are very sharp. It is not advisable to use such soaps upon delicate skins, as they induce redness of appearance, and give the skin a tendency to roughen or chap, especially when exposed to the wind.

619. To Pulverize Hard Soap

619.    To Pulverize Hard Soap. Hard bar soap should be scraped or planed into fine shavings, dried in the sun, or by heat, thoroughly, and then pounded or crushed! After this, it should be placed in a bowl or kettle, and a small cannon ball should be used to pulverize it; when thoroughly pulverized it may be sifted through a very fine sieve.

620. To Analyze Soap

620.    To Analyze Soap. Take a small portion of the soap, place it in a suitable vessel (a beaker glass), add ether to it, and next acetic acid in a somewhat smaller quantity. The liquid will separate, after a while, into two distinct layers, the upper of which contains in solution the fatty acids, while the lower layer contains the alkalies and salts, and such substances as might happen to be insoluble in the two fluids just named. By means of a pipette, the fluids are separated from each other. The ethereal solution is poured into a previously weighed beaker glass, and the ether evaporated upon a water bath, and next again weighed with the fatty acids it contains. The aqueous acetic acid is evaporated to dryness, and the quantity of alkali determined according to well-known methods. (See No. 586 (To Estimate the Percentage of Caustic Alkali in a Caustic Soda or Potash)).

621. Analysis of Soda and Potassa Lyes

621.    Analysis of Soda and Potassa Lyes. The following tables will show at a glance all the practical information necessary for analyzing or testing the strength of lyes, either simple or caustic, as well as affording thorough guidance in mixing or adjusting the strength of lye for any specific purpose.

622. Lorm'e's Tables

622.    Lorm'e's Tables. The following tables are used to transform stronger lyes into weaker of a definite degree of strength, and are by Mr. Euge`ne Lorm'e.

The first column at the left of each table shows the quantity and the degree of the lye to be diluted.

The second indicates the quantity of water to be added to the lye.

The third gives the amount of the lye obtained by the admixture of both liquids.

The fourth exhibits the degrees of Baum'e's areometer of the lye.

623. Table showing the different Areometric Degrees

623.     Table showing the different Areometric Degrees resulting from a mixture of 10 gallons of soda lye, of 36 degrees Baum'e, with quantities of water varying from 10 to 90 gallons.

Number of gallons of Lye of 36 degrees.

Number of gallons of Water.

Number of gallons of obtained

Lye.

Degrees of

Baum'e of the mixture.

10 10 10 10 10 10 10 10 10

10 20 30 40 50 60 70 80 90

20 30 40 50 60 70 80 90 100

23°

17

14

12

10

9

8

71/4

63/4

10 gallons of lye, of 36 degrees Baum'e, weigh 1121/2 lbs.