545. In making cream of tomato soup, soda is added to the tomatoes before the milk is, so that the milk will not curdle How does the soda prevent curdling? 546. The soda makes the soup froth up. 547. A wagon squeaks when an axle needs greasing. 548. Seidlitz powders are mixed in only _half_ a glass of water. 549. The work of developing photographs is all done with a ruby light for illumination. 550. Coal slides forward off the shovel into a furnace when you stop the shovel at the furnace door. CHAPTER TWELVE ANALYSIS SECTION 58. _Analysis._ How can people tell what things are made of? If it were not for chemical analysis, most of the big factories would have to shut down, much of our agricultural experimentation would stop, the Pure Food Law would be impossible to enforce, mining would be paralyzed, and the science of chemistry would almost vanish. Analysis is finding out what things are made of. In order to make steel from ore, the ore has to be analyzed; and factories could not run very well without steel. In order to test soil, to test cow's milk, or to find the food value of different kinds of feed, analysis is essential. As to the Pure Food Law, how could the government find out that a firm was using artificial coloring matter or preservatives if there were no way of analyzing the food? In mining, the ore must be assayed; that is, it must be analyzed to show what part of it is gold, for instance, and what part consists of other minerals. Also, the analysis must show what these substances are, so that they can be treated properly. And the science of chemistry is largely the science of analyzing--finding out what things are made of and how they will act on each other. The subject of chemical analysis is extremely important. But in this course it is impossible and unnecessary for you to learn to analyze everything; the main thing is for you to know what analysis is and to have a general notion of how a chemist analyzes things. [Illustration: FIG. 186. The platinum loop used in making the borax bead test.] When you tested a number of substances with litmus paper to find out which of them were acids, you were really doing some work in chemical analysis. Chemists actually use litmus paper in this way to find out whether a substance is an acid or a base. THE BORAX BEAD TEST. This is another chemical test, by which certain substances can be recognized: EXPERIMENT 113. Make a loop of wire about a quarter of an inch across, using light-weight platinum wire (about No. 30). Seal the straight end of the wire into the end of a piece of glass tubing by melting the end of the tube around the wire.