Universal Indicator Solution

Third Rail System

By the time you've had a smartphone (especially an iPhone) for more than a couple of days, you've learned, possibly the hard way, that your phone needs to be charged every night. For those who can't or don't want to deal with that, a range of companies have created battery cases that provide some extra on-the-go juice. These cases can as much as double the iPhone's battery life, but they come at a cost: They typically take the slim, svelte iPhone 4 and make it a blocky, bulky brick. Third Rail Mobility, a new company, takes a fresh approach, making a battery case in two parts: the case, and the battery. When you don't need the extra power, the case is slim, light, and protective. When you need some juice, simply snap on the battery (or a couple of them), and power up your phone. The modular solution is a clever one, and the Third Rail System ($89.99 direct) is an ideal choice for most users, but it doesn't provide enough extra juice to unseat our Editors' Choice iPhone 4 battery case, the Mophie Juice Pack Air ($79.95, 4 stars).

Design
Without its battery attached, the Third Rail System looks a lot like any other case for the iPhone 4 (and it only works with the iPhone 4). It's extremely thin and light, adding just 0.1 inches to the iPhone's depth, and 0.8 ounces to its weight. The only noticeable size change, actually, is that since the case needs to plug into the iPhone's dock connector, it makes the phone about an inch taller. The case is all black, and made of two pieces; the top snaps off to make it easier to slide the iPhone in. There are cutouts for the iPhone's volume controls and camera lens, and on the bottom, there's a micro-USB port for charging and syncing the phone while it's in the case. An on/off switch lets you stop the iPhone's battery from charging via the case. I don't know why you'd want to do that, but it's there if you do.

The battery itself is petite as well, a small bump about half the height of the iPhone. It weighs 1.4 ounces, adds 0.3 inches to the device's depth, and locks into place via four small feet that fit into notches on the back of the case. On the battery itself are a battery-level indicator, and two ports (one micro-USB and one proprietary) that let you charge the battery without the case, or use the battery to charge other devices via USB. You could, conceivably, buy a few batteries ($59.99 each) and swap them in and out on the case for extra juice. There's an included adapter that lets you plug any USB cable into the battery, making the Third Rail System something of a universal charger.

Element Test Notes For O-Level Chemistry

Testing for Anions ( Negative Ions ) : Carbonate ( CO3 2- ), add dilute hydrochloric acid ,result is effervescence , carbon dioxide produced ( test with limewater )

 

Chloride in solution ( Cl- ) , acidify solution with dilute nitric acid then add aqueous silver nitrate , result is white ppt. of silver chloride formed. ( ppt soluble in ammonia solution )

 

Bromide in solution ( Br- ) acidify solution with dilute nitric acid then add aqueous silver nitrate , result is cream ppt. of silver bromide formed , ( only slightly soluble in ammonia solution )

 

Iodide in solution ( I- ) acidify with dilute nitric acid then add aqueous silver nitrate , result is yellow ppt of silver iodide , insoluble in ammonia solution OR acidify with dilute nitric acid then add lead nitrate solution , result yellow ppt. of lead iodide formed.

 

Sulphate in solution ( SO4 2- ) acidify solution with dilute hydrochloric acid then add barium chloride solution , OR acidify solution with dilute nitric acid then add barium nitrate solution , result for both is white ppt of barium sulphate formed.

 

Nitrate in solution ( NO3 – ) make alkaline with sodium hydroxide solution then add aluminium foil ( or Devarda’s alloy ) and warm carefully , result is Ammonia gas is given off ( test with moist red litmus ).

Testing for Metal ions by burning : Sodium (Na+) burns giving yellow flame.

 

Potassium (K+) burns giving lilac flame ( pale violet ).

 

Calcium (Ca2+) burns giving brick-red flame.

 

Lithium (Li+) burns giving crimson flame.

 

Copper (Cu2+) burns giving a blue-green flame.

 

Barium (Ba2+) apple-green (chartuese , close to lime a bit I think ).

Testing for Positive ions in solutions by adding sodium hydroxide: Ammonium (NH4 +) , ammonia produced on warming.

 

Copper(II) (Cu 2+) , light blue gelatinous ppt. of copper hydroxide ( insoluble in excess sodium hydroxide ).

 

Iron(II) (Fe 2+) , green gelatinous ppt. of iron(II) hydroxide ( insoluble in excess ).

 

Iron(III) (Fe 3+) , rust-brown gelatinous ppt. of iron(III) hydroxide ( insoluble in excess ).

 

Calcium (Ca 2+) , white ppt of calcium hydroxide ( insoluble in excess ).

 

Magnesium (Mg 2+) white ppt. of magnesium hydroxide ( insoluble in excess ).

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